Charging issues

[hbn7hj]

1 lithium battery, 1 60 amp lithium charger. Charge current 59 amps
2 lithium batteries in parallel, 2 60 amp lithium chargers in parallel. Charge current 95 amps.
4 lithium batteries in parallel, 2 60 amp chargers and 1 80 amp charger in parallel. Charge current is 110 amps.

Charging voltage stays at 13.8 volts till full when it will increase to 14.5.

I assume the reason for the charge rate not nearing 200 amps is due to the interaction of the parallel chargers. The charger supply voltage from the 4KW generator increases as each charger is added peaking at 124 volts so I don’t think it is a supply voltage problem.

110 amps is OK but what would it take to get a higher charge current? One charger rather than 3? I’m not really interested in separating the batteries during charging.

Does anyone know what is happening to keep the charge rate low?

I sent the question to Battleborn. Will post their answer if I get one.

 

[GallenH]

Are you currently modifying your hybrid setup?

 

[hbn7hj]

Are you currently modifying your hybrid setup?

No. I added two 100AH Battleborn batteries to my class C to support a compressor refrigerator conversion that I haven’t done yet. The original 3-way propane one is working fine. It doesn't work very well in 110F but I’m at 10,000ft with no problem.

The only change I can see for the class B is a second lithium battery but I’d put the compressor fridge in first to see if I needed it.

 

[booster]

I certainly would think it would be the parallel chargers having a lot to do with it.


If the chargers don't have exactly the same voltage output and the resistances in the wiring to batteries exactly the same, they would be putting different voltages on the batteries. Different voltages would mean that lowest voltage charger is essentially shut off be the higher voltage one unless the battery voltage is low enough to drag all the chargers down to low enough voltage to match.


We we see this all the time in our setup when driving and charging with the alternators and the solar on at the same time and in the sun. If the batteries are quite low both will contribute but once the battery voltage nears absorption the alternator does less as it runs at slightly lower voltage. When I switch the alternator to float it will be putting out nothing to the coach batteries at all, or to the van, if the solar can handle that much current. At that point I need to shut off the alternator charging to the coach or the solar won't finish the top off charging.


You might want to try turning the chargers on one at at time, in various orders, to see how much each charger contributes as they stack in different combinations. Might be very interesting results.

 

[markopolo-ClassB]

Booster explained it nicely. :thumbup:

I'm guessing the goal is to reduce generator runtime. As Harry surmised, one very high output charger would be best.

Given the equipment noted then the least expensive way to get up to 140A would be to group the batteries into two pairs and add a battery disconnect between the two groups. Connect the 80A charger to one group and the 60A charger to the other group. Use the disconnect when fast charging.

 

[booster]

Another thing to consider, but that I haven't ever really tested, would be how the quite high AC power requirement could be affecting the chargers which may react differently to low input voltage from sag under load. A 100 amp charger is going to take about 1/2 of the capacity of a 30 amp AC RV input, so trying to get to 200 amps is going to be really loading down the input, or the output from the generator. 200 amps at 14.4v absorption voltage is over the rated 2800 watts the Onan has to offer, and that doesn't include the inefficiencies of the charger(s) or any other use.


Most chargers also lose output when they get hot from running hard, maybe 5-10% drop?

 

[hbn7hj]

Yep, this is on a class C with a 4KW Onan which increases to a 124 volt output as the chargers are switched on but the output voltage doesn't increase to over 13.8 volts till charging nears completion.

I guess what Im looking for is a way to fool it to bulk charge at 14.4 volts.

One charger alone with four batteries approaches the charger rating but still charges at 13.8 volts. I haven't isolated it to one battery again to see what happens.

Maximum power required would be around 3400 watts. The 1100 watt microwave fails when also charging batteries, as expected.

 

[booster]

You may be looking at an issue with the chargers being too "smart", which I have found happens a lot. A bunch of the chargers will take a look at the voltage of the battery or bank and decide if they should do a charge cycle or go right to float. The fact that your chargers are staying at the same voltage regardless of output may indicate they are in float, or at least some of them.


The chargers I have seen generally will go to float if the voltage is above something like as low as 12.6v, some want 12.7 or 12.8v. If you have the lithium in the system, it is likely always higher than that unless very low in charge.



Most of the chargers I have seen could be fooled to go into absorption stage by artificially getting the voltage down low enough. On lead acid systems is can be pretty easy by turning on high load things, but could be a lot harder on the lithium combo setup. Once the charger is in absorption and up to voltage or at least above resting voltage, you can turn off the load in most cases.


With the combo system, you may need to take the lithium batteries out of the system until the chargers get up into absorption mode. You may still have to turn on the microwave to drive down the voltage, but with the lithium out of the way, it may work for you.


Once the chargers are in absorption they should be running on the charge algorithm or timer and stay there as a normal full charge, so you should be able to turn the lithium back on at that point.

 

[hbn7hj]

These are lithium chargers only and are “smart” which I’m sure is the problem. They don't see the FLA batteries which have their own “smart” charger.

Don't really want to do it but I will at least have to test splitting the banks and see what happens. 95 amps plus 80 amps would give a charge rate of 175 amps which is better than what I am getting now.

 

[hbn7hj]

Separating the two banks of two brings the charging rate up to 165 amps. 70 amps out of the 80 amp charger and 95 amps out of the two 60 amp chargers. At the moment I don’t have a convenient way to separate the two. Certainly an improvement.

 

[cruising7388]

I certainly would think it would be the parallel chargers having a lot to do with it.


If the chargers don't have exactly the same voltage output and the resistances in the wiring to batteries exactly the same, they would be putting different voltages on the batteries. Different voltages would mean that lowest voltage charger is essentially shut off be the higher voltage one unless the battery voltage is low enough to drag all the chargers down to low enough voltage to match.


We we see this all the time in our setup when driving and charging with the alternators and the solar on at the same time and in the sun. If the batteries are quite low both will contribute but once the battery voltage nears absorption the alternator does less as it runs at slightly lower voltage. When I switch the alternator to float it will be putting out nothing to the coach batteries at all, or to the van, if the solar can handle that much current. At that point I need to shut off the alternator charging to the coach or the solar won't finish the top off charging.


You might want to try turning the chargers on one at at time, in various orders, to see how much each charger contributes as they stack in different combinations. Might be very interesting results.

I think that the charging sources recognized by the batteries depends on the modes of the chargers. If the chargers are in the absorption mode the batteries recognize only the charger producing higher voltage. But if the chargers are in the bulk (constant current) mode, the batteries will recognize the output from both chargers.

 

[booster]

I think that the charging sources recognized by the batteries depends on the modes of the chargers. If the chargers are in the absorption mode the batteries recognize only the charger producing higher voltage. But if the chargers are in the bulk (constant current) mode, the batteries will recognize the output from both chargers.

That is where the other factors of cable length and such come in, also, I think. Bulk and absorption are the same mode in most chargers, for the most part it appears, as they set a max voltage at the absorption level and then produce to their maximum output to try to get there. Before the chargers get to full voltage they will be producing at max output, but one may get to max before the other and start tapering sooner.


The recognizing thing is not that the batteries recognize the chargers, it is that the chargers see the the battery voltage and use that to determine what stage to go into. In the case of this discussion, the lithium batteries are likely holding up the voltage of the entire bank to higher than the normal rested voltage of AGM batteries, so the chargers think they are dealing with full batteries and go to float instead of full charging in bulk/absorption. At least I think that is what is happening. At the lower voltage the AGMs in the system will not accept as much current, so max output can't be used from the chargers.


These were stated to be "lithium" chargers, but what we have seen is that that designation just means they have a special absorption voltage setting for lithium in an other wise AGM charger, I think, so all the AGM "smartness" is probably still there.

 

[markopolo-ClassB]

It becomes easier to understand when referencing specific voltages rather than modes. It's all about how much current it takes to support a particular system voltage at continually increasing state of charge. If charger A maxes out at 14.44975V and charger B maxes out at 14.399001V then the chargers share the load (likely not precisely equally) until the system voltage reaches 14.399002V. Charger B can't assist again until the system voltage drops to 14.399001V or less.

 

[hbn7hj]

I split the battery packs and chargers by breaking the 12 volt line between them. Supply voltage is at 125 volts. When the second charger is turned on the first one reduces it's charging rate with supply voltage staying at 125 volts. How can that be? Maybe something in the ground so Ill break that for a test.

Anyhow, I’m on the road and it takes 45 minutes to bring everything to 100% after a below freezing night so I’ll live with that and work with it when I get back. Apparently I need two 100 amp dumb chargers set at 14.5 volts.

No net access where Im parked.

 

[hbn7hj]

Battleborn says the four lithium batteries should accept 200 amps. Call Progressive Dynamics to find out why 200 amps worth of chargers are not delivering.

When I figure it out I’ll let you know. A 200 amp charge rate from the generator would be nice.

 

[markopolo-ClassB]

Normal PD chargers would run as cruising7388 mentioned. The first would go to bulk mode but the others might not.

PD lithium chargers should all be in their 14.6V mode until 14.6V is reached, at least that's what would be expected.

Iota's IQ4 synchronizes parallel Iota chargers ->
https://www.iotaengineering.com/pplib/Series_and_Parallel_Charging.pdf

It will be interesting to hear what PD replies.

 

[booster]

Normal PD chargers would run as cruising7388 mentioned. The first would go to bulk mode but the others might not.

PD lithium chargers should all be in their 14.6V mode until 14.6V is reached, at least that's what would be expected.

Iota's IQ4 synchronizes parallel Iota chargers ->
https://www.iotaengineering.com/pplib/Series_and_Parallel_Charging.pdf

It will be interesting to hear what PD replies.

I have never had a PD charger, but from the literature it appears that they always do a 4 hour charge cycle when you plug in so all would go to bulk/absorption at that point if that is correct. If the PD does the all to common voltage check to determine if it should run a charge cycle, what Marko describes certainly could happen if one charger was a bit quicker to start than the others because it would show higher voltage and the others would go to float directly.


It will be interesting to see what they say.

 

[booster]

From this statement, if I am interpreting it correctly, I think a PD would only go into "boost" mode if the battery is low, so not every cycle. The charge diagrams don't indicate that possibility, though.

The optional Charge Wizardautomatically senses when a battery has a very low state of charge and automatically selects its BOOST MODE of operation. BOOST MODE increases the voltage of a PD9100 Series converter/charger to 14.4 volts.

PD does seem to say they have no trouble with parallel chargers, though, even to a 12/24v bank.


https://www.progressivedyn.com/marine/


Diagrams at the bottom of the page

 

[markopolo-ClassB]

The PD charger for lead acid batteries that I have does check for something at startup. I don't know if it's voltage or resistance or output current. It can start in 13.6V mode. If it doesn't see a battery or is somehow tricked into not seeing a battery it goes straight to 13.6V mode. However, I'd expect 14.4V mode if system voltage was low.

 

[markopolo-ClassB]

Harry has lithium chargers.

This note is in the Inteli-power lithium manual:

The system was designed to sense voltage on the battery and will taper the charging current as the battery becomes charged.

Current tapering is a natural occurrence as a battery nears a voltage setpoint (edit to add: at least that's how every charger I've ever had, even the most basic, interacts with a battery). The note in the Inteli-power lithium manual seems to indicate that they designed the charger to also taper current in addition to the naturally occurring/expected tapering.