Field Test: lead acid and lithium hybrid battery system

[hbn7hj]

Objectives:
1 Two totally separate power and charging systems. Lead Acid and Lithium. Lead acid is slow to charge and difficult to use the full capacity but works very well below freezing. Lithium can use more of the capacity, charges rapidly, but does not handle temperature extremes well.

2 Test whether a fully charged lithium battery connected to a battery to battery charger can charge a lead acid battery to 100%, overnight, after being brought to 80% charge by generator.

3.Determine how the two different batteries can be joined together to power the RV.

It is not necessary to respond to this thread to keep it going. Comments welcome. I will add progress information as I have it.

Components:
60 amp Lithium battery charger
Progressive Dynamics PD9160AVL

40 amp battery charger for lead acid batteries
Xantrex Smart Charger 2

Battery Switch
Blue Sea Systems 350 amp 9100E

Battery
BattleBorn 100 ah Lithium with BMS located inside the coach
for temperature stability. No battery heaters needed
2 Trojan T-105 flooded lead acid 6 volt 225 ah 5 years old.

Battery Monitor
Bogart Engineering TM-2030 Boondocker (lithium)
100 amp shunt.
Bogart Engineering TM-2025 (lead acid)
100 amp shunt.

Battery Tray
Attwood Marine Series 29/31

Battery to Battery charger
Kisae Technology ABSO DC to DC Battery charger
DMT1230 12 volt 30 amp

50 amp toggle switch from Backwoods Solar.

Generators
4kw Onan Microquiet
1kw Honda EU1000i on propane.

Solar
200 watts. Not a major player in this excercise

 

[hbn7hj]

First observation is the Blue Sea battery switch is too big for a class B. It requires a 3 3/4" mounting hole. This installation is on a class C and I plan to add two more batteries and an inverter later on. I think there are smaller ones out there and high current toggle switches could be used.

Second observation is the battery strap on the battery tray does not get tight enough and I will replace it with a cargo strap. Battery movement could fatigue wiring.

I don't have room for any of this stuff on my B. Will figure that out at a later time.
Harry

 

[eric1514]

Could you please draw a simple diagram of how everything is connected? Thanks.

 

[hbn7hj]

I can't make a drawing but Booster can. He has already posted one on another thread that is close. Let me get it hooked up first.

Booster, my email is hbn7hj at AOL dot com to sort out the schematic, if interested.

The idea for this is Booster's and GeorgeRa gave us the lead for the B to B charger. It appeals to me because I need more battery capacity, I don't want a lithium only system due to battery heaters and initial cost, I don't want AGM batteries. With this I can add lithium batteries if I want them as I have room for two more.

Temperature is not a problem as the lithiums are in the living space. For the cost of a battery, charger, and switch we will be in the lithium world and can decide if we want to stay there.

The next problem will be charging time. The RV will not be moving so we will see what happens with generator run time. Solar will help, of course.
Harry

 

[hbn7hj]

All wired up. Those of you that want a schematic will have to draw your own. each battery type has it's own dedicated charger. The lithium battery goes to the battery to battery charger through a toggle switch. The output of the B to B charger goes to the lead acid battery through a switch. The control input of the B to B charger is tied to the positive post of the lithium battery. The marine battery switch is not necessary yet.

The battery to battery charger is powered by the lead acid battery.

I have not made it possible to short the two batteries together yet.

The battery monitor went live today. That is it for now. I have guests the next four days and won't mess with it.

I hit black ice under snow on the way up here. Ten wheels sliding! Didn't hit anything and don't wanna do that again!

 

[hbn7hj]

It appears the Kisae unit will do exactly what we hoped. At the present time the Satelite Tv is running, both batteries are at the 97% state of charge.

The Lead Acid battery is charging at 14.4 volts and 8 amps. The lithium is discharging at 17 amps. The sat TV setup will normally draw 3 to 4 amps.

The implication is there is an efficiency issue but we will look at that at a later time.

So far so good!
Harry

Further checking shows 2.5-3 amps leaves the lithium battery that is not accounted for. A better check would be to compare watts. Haven't done that yet.

 

[hbn7hj]

With a little evolution this electrical mod becomes one of the most useful yet.

With a few wiring changes coach power can be switched from Lithium to Lead/acid. Solar charging goes to the battery selected for coach power and each battery has it's own charger powered by the generator.

It doesn't take too long to realize a lithium battery is "twice" the battery of lead/acid. Lithium charges to 100% more rapidly, doesn't need ventilation, and provides power at a higher voltage throughout the discharge cycle. The serious drawback is the temperature sensitivity. I'm often in freezing temperatures so this is important.

Might as well keep the lead/acid batteries in the outside rack since they can handle the temperature swings. Lithium is mounted inside.

This is the way I use them. Both batteries are at 100% by the early evening. Switch to lithium for the evening power drain. Lights, computers, TV, furnace or vent fans run on lithium. At bedtime, switch to lead/acid which is at 100% with plenty of power for the furnace.

Next morning the lead/acid battery is at a 80-90% state of charge, the lithium is as it was left the night before, 46-79% depending on TV usage.

With a 60 amp charger lithium charges at less than a minute for each percent state of charge. Starting at 88% L/A and 69% Li a generator run of less than 30 minutes gets you 100% lithium and 94% L/A. Solar brings the L/A to 100% by evening for the next cycle.

Note that the DC to DC charger plays no part if the sun is out but will be a good backup in bad weather. The hero of this install is the marine battery switch.

It works so well I'll try to put it in the class B. Lithium battery in the water heater compartment and the lithium charger in with the lead/acid charger. Marine switch on a bracket in with the lithium battery.

 

[booster]

Hi Harry, I have been watching all your adventures closely and it is all very interesting!

The fact that getting the DC to DC charger in the system took care of, it appears, essentially all the downsides that we thought might happen in the two chemistries interactions with each other really opens up lots of options for how different folks might want to use the system.

The way you are using it right now is somewhat different than what the very original idea was back in the original thread. Having the solar gives you an advantage that makes the ability to charge the AGM to the final full less of an issue, but having the lithium fast changed in the morning, to run off during the day, allows the AGM to be filled by the solar.

Have you had a chance to test the original premise, which you have listed as number two in the your first post? This would be for the non solar type applications where probably the largest benefit would be to use the lithium to do the final, long period, charging of the AGM to totally full, perhaps during the overnight hours after a short genny run before bedtime. Based on what you have found out about how well all the stuff plays together, my guess is that there is a very high probability it will work very well in this method also.

It looks like the possibility of, perhaps, a 75ah lithium with about 150ah of AGM, or a bit more of each or less of each based on use, could give performance close to what a very much more expensive all lithium system would, especially without solar. If you have an engine generator in the system, you would be able to replace 75ah in the lithium battery in under 1/2 hour of driving or idling and then it could take care of finishing off the AGMs. Generator would take a bit longer depending on the size of the shore charger, but a 100 amp charger which is getting more common would also do very well, very quickly, off the standalone generator.

Great information, Harry, you have taught us all a lot, and also given us all a bunch of new options in more moderate cost, user friendly, more capable, systems.

 

[hbn7hj]

Have you had a chance to test the original premise, which you have listed as number two in the your first post? This would be for the non solar type applications where probably the largest benefit would be to use the lithium to do the final, long period, charging of the AGM to totally full, perhaps during the overnight hours after a short genny run before bedtime. Based on what you have found out about how well all the stuff plays together, my guess is that there is a very high probability it will work very well in this method also.

At 12:30 today with the L/A battery at 86% and Li battery at 100% we turned solar off and turned on the DC to DC charger. Initial charging current was 27.9 amps into the L/A and 35 amps out of the Li. Three of those amps were supporting the coach. Three and a half hours later the L/A is at 98% and still charging at 5 amps.

During that time I did run the generator with the Li charger on. The increase in Li battery voltage did increase the charging voltage of the L/A. That I didn't expect. Also it seemed the DC to DC charger was in lesser rate mode like absorption or float. Maybe there is a way to force it to stay in bulk.

Bottom line is it works exactly like we had hoped though maybe not as fast. It was 31F here last night and I need both batteries at 100% so I stopped it. When it warms up I can give it a longer test from a lower state of charge.

One surprise was when I turned solar on to the Li battery while it was charging the L/A battery I saw 13.5 amps. I have never seen over 7 amps from solar to the L/A battery. 13.5 amps is around 160 watts on a thin overcast day with the panel not perpendicular to the sun line. That is really good for a 200 watt panel. I guess a Li battery is easier for solar to charge or the concurrent battery drain to the DC charger had something to do with it.
Harry

 

[hbn7hj]

Time to put this in a class B. I don't have access to my Chevy Roadtrek 190. Those of you that do. What are the dimensions of available space in the hot water heater cabinet? Also we need the smallest marine type battery bank switch(1, 2, and both) that can handle 100 amps.
Harry

 

[booster]

No help here on the water heater space as our 2007 is different than your earlier version.

I haven't seen anything that I recall as small as 100 amps in the selector switches. When I was looking at when I built the last system for our van, the Blue Sea Mini was close to smallest at just under 3 X 3 and about 3.3" knob to back. IIRC, the smallest I found was the Marinco (and other private label) ones like this.

https://www.amazon.com/BEP-701-Batt...717723&sr=8-3&keywords=marinco+battery+switch

They are about 1/4" smaller in all dimensions than the Blue Sea.

 

[hbn7hj]

The BEP switch ought to do it.

For you guys that know more than I do. All of the chargers and inverters have a chassis ground lug that they say not to short to the ground terminal. I haven't hooked any of them up but I suspect they are there for an important reason. What is the reason and what gauge wire should I use?

Any guinea pigs ready to add a lithium battery to a Sprinter? Find inside battery space, switch and battery monitor location and $1500 and let us know the possibilities.
Harry

 

[Gryphon-ClassB]

Time to put this in a class B. I don't have access to my Chevy Roadtrek 190. Those of you that do. What are the dimensions of available space in the hot water heater cabinet?
Harry

Not sure which dimensions you're looking for. In my 190, the cabinet with the water heater is roughly 12 inches tall, 24 inches deep, and 20 inches wide (these are all approximate measurements - I didn't have a tape measure in the RV, so I used an 8.5 x 11 piece of paper as my "ruler"). But the wheel well protrudes into the space a bit, so near the van wall along the floor, you've probably got more like 16 inches of width.

If you want to try to squeeze something into the free space in that cabinet without disturbing anything else, you're looking at the space in front of the water heater which is only 4 or 5 inches deep, and roughly 12" tall by 15" wide.

If you pull out the water heater but keep the water pump & the rest of the plumbing, that would increase the available space to something like 24" x 12" x 15".

 

[hbn7hj]

Thanks for the dimensions. The smallest dimension on a Battleborn battery is around 7 inches. I'll look at other vendors. Maybe I can clear out the bay aft of the electrical compartment and put the Chargers in the water heater compartment.

 

[booster]

The BEP switch ought to do it.

For you guys that know more than I do. All of the chargers and inverters have a chassis ground lug that they say not to short to the ground terminal. I haven't hooked any of them up but I suspect they are there for an important reason. What is the reason and what gauge wire should I use?

Any guinea pigs ready to add a lithium battery to a Sprinter? Find inside battery space, switch and battery monitor location and $1500 and let us know the possibilities.
Harry

I think you are talking about the equipment grounding lug that is normally on the outside of the case of the inverter, and is not the 12v negative connection? If so, this is just the equipment ground, or the the connection from the inverter chassis to ground if something bad happens inside the inverter. In RVs, the negative for the 12v is normally the chassis of the van, and the chassis of the van is also the safety ground for the DC and for the AC wiring, so pretty weird that all are connected together.

In the real world, I think the only thing the warnings mean, and our Magnum doesn't even have a warning about the equipment ground, is that they don't want you to use the DC negative connection for the safety ground wire and they don't want you to use the safety ground lug for the DC negative. The goal is to have two separate current paths, so not combining them until they get to the van chassis ground is what they want, I think, but phrase poorly sometimes. For size, you usually want to be able to handle as many amps as the fusing for the DC input to the inverter will allow. No worry about voltage drop, just temp, so can be bare and fairly small. IIRC, I have a #2 bare on our 2000 watt inverter. On ours, the 12v negative, and the bare safety ground both travel about 18" and connect to the van chassis.

 

[booster]

I made some additions and changes to one of my original possibility wiring diagrams based on Harry's description of how he has his setup wired. Should be pretty close I hope, and Harry can jump in and get it fine tuned if needed.

 

[hbn7hj]

That ought to do it. We have a 50 amp fuse between the Lithium shunt and ground. Lithium charger ground current does not go through the fuse. Kisae wants a 30 amp fuse on the power to the charger. We chose not to do it. Safety suggestions appreciated.

We have a second battery, second lithium charger, 1500 watt Samlex hardwired inverter and a transfer switch yet to go. Probably sometime in June.

Use procedure is changing. Right now the following is being tried.

Early evening both batteries at 100%
Evening current draw on lithium.
Switch to flooded lead acid at bedtime.
Morning start generator and charge both batteries. Stop when lithium is at 100%. Lead/acid is then around 85%
Solar charge current to lithium
Turn on DC to DC charger.
Early evening short generator run to bring lithium to 100% Lead/acid is at 100%

The solar panel seems to be able to put much more current into the lithium battery than the lead/acid battery, Have yet to compare that to the efficiency loss of running it through the charger but my solar controller is dumb whereas the charger has three stages.

We will see how it works. Thanks to all for the help.

 

[booster]

Very nice, I think we have a winner here

I think you have plainly proved that the AGM batteries can be taken care of very well, getting to 100% full regularly, with much shorter, quicker, generator runs compared to the muli-hour runs that would be needed to charge the AGM full directly. Of course you get a boost from the solar, but from what you are seeing, I think it would also be working well without the solar.

Not surprised that the solar will put more into the lithium than the AGM at 85% as you are well into the acceptance tapering of the AGM by then

 

[Bud-ClassB]

Very nice, I think we have a winner here

I think you have plainly proved that the AGM batteries can be taken care of very well, getting to 100% full regularly, with much shorter, quicker, generator runs compared to the muli-hour runs that would be needed to charge the AGM full directly. Of course you get a boost from the solar, but from what you are seeing, I think it would also be working well without the solar.

Not surprised that the solar will put more into the lithium than the AGM at 85% as you are well into the acceptance tapering of the AGM by then

"...I think we have a winner here...."

Is this a commercially viable product?

Bud

 

[hbn7hj]

Dunno, We don't know what happens when the lead/acid is discharged, lithium is fully charged and the switch left on "both." It isn't dumb proof yet. The need for two battery monitors would exclude some customers who wouldn't push buttons to see what is going on. A solar vendor would probably have more insight as to whether it is a commercially viable install.

Percent full numbers on battery monitors are just guesses and sometimes they get way off. Intervention required.

In my mind your grandmother has to be able to run it and we aren't there.

For us, $1500 gets you into the lithium world, more than doubles your available amp hours since you will more often use the 80-100% charge capacity of the lead/acid and you have no lithium temperature sensitivity.
Harry