in roadtreks defense-when my inverter/charger on my microwave lights ,tv,and blue ray player all go on. i never worry about unplugging
do they have a 6000 watt one?
in roadtreks defense-when my inverter/charger on my microwave lights ,tv,and blue ray player all go on. i never worry about unplugging
do they have a 6000 watt one?
Yes, I would say that's about right. I never received any power saver info from them either by e-mail or phone conversations.
the e-mail came 2 days ago. do they have your e-mail. you may get it later however since it's now posted look at the supplement here
BBQ-ClassB
Senior Member
cruising7388
Senior Member
What Volt Start problems are you experiencing?
I reread the Roadtrek PDF a couple of more times, and it seems to fall into the category of lots of confusing calculations based on shaky starting points and data. I doubt many everyday Roadtrek shoppers would be able to adequately determine much from it, and would just look at the conclusions, which have to be correct because of all those fancy calculations.
For giggles, I tried to do a much simpler, real world, calculation for the AGM to Ecotrek comparison.
Assume--200ah capacity for both AGM and Ecotrek---80% drawdown for both so 160ah usable---100ah per day of battery use (used uniformly over the day) or 4.2ah per hour---AGM at 1% per month capacity loss (.0028ah per hour), Ecotrek at 5 amps (5ah per hour)---
That puts the AGMs using 4.2028ah per hour and the Ecotrek using 9.2ah per hour.
The AGMs will run for 38.07hrs to discharge to 20% SOC and the Ecotrek will run for 17.39 hours to get to 20% state of charge
Bottom line the AGMs will run 2.2 times longer than the Ecotrek will before needing recharging. The Ecotrek won't make even one full day.
Even if you use the, now questionable, 50% max on the AGMs, you would get 23.8 hrs of run time, which is still 1.37 times the Ecotrek run time.
If you use the very popular 220ah AGMs the run times would be 41.9hrs to 20% SOC and 26.17hrs to 50% (in the Roadtrek example they used 2000 watt-hrs which would be only 167ah at 12v which is tiny for a pair of 6v AGMs).
I don't suppose Roadtrek would want to publish anything that said your Ecotrek couldn't even run for 1/2 the time of the same size AGM battery, as the customers would actually be able to understand that, but it appears that would be much more accurate. :silent:
For giggles, I tried to do a much simpler, real world, calculation for the AGM to Ecotrek comparison.
Assume--200ah capacity for both AGM and Ecotrek---80% drawdown for both so 160ah usable---100ah per day of battery use (used uniformly over the day) or 4.2ah per hour---AGM at 1% per month capacity loss (.0028ah per hour), Ecotrek at 5 amps (5ah per hour)---
That puts the AGMs using 4.2028ah per hour and the Ecotrek using 9.2ah per hour.
The AGMs will run for 38.07hrs to discharge to 20% SOC and the Ecotrek will run for 17.39 hours to get to 20% state of charge
Bottom line the AGMs will run 2.2 times longer than the Ecotrek will before needing recharging. The Ecotrek won't make even one full day.
Even if you use the, now questionable, 50% max on the AGMs, you would get 23.8 hrs of run time, which is still 1.37 times the Ecotrek run time.
If you use the very popular 220ah AGMs the run times would be 41.9hrs to 20% SOC and 26.17hrs to 50% (in the Roadtrek example they used 2000 watt-hrs which would be only 167ah at 12v which is tiny for a pair of 6v AGMs).
I don't suppose Roadtrek would want to publish anything that said your Ecotrek couldn't even run for 1/2 the time of the same size AGM battery, as the customers would actually be able to understand that, but it appears that would be much more accurate. :silent:
wincrasher
Senior Member
I guess I missed something a while back - where is this drawing down to 20% is OK on AGMs coming from?
The latest discussion is here:
http://www.classbforum.com/forums/f23/another-view-of-the-50-agm-discharge-limit-5595.html
It all got started originally in one of the lithium threads, which is linked in the above one.
wincrasher
Senior Member
Well, that looks like nonsense to me. According to the table, the life cycles drop almost in half. While they're working, yes I guess the available aH doesn't drop that much (12%), but the end result is dead batteries in half the time as treating them per the guidance.
what was actually discussed was that the actual battery penalty in battery lifespan was not that great going to 80 instead of 50. It was much greater the higher you stayed above 50 but 50 and below itself was not so great to lifespan
wincrasher-you miss the point. the cost of lithium and agm.
using agm to 80 and having to replace more often is a viable strategy instead of getting into the whole lithium thing.
The number of cycles you get may drop in half, but the total energy you can store and then recover is much less than that, and the energy is what counts. What that means compared to cycles is that if you do two cycles of 40% discharge, it is equivalent to one cycle of 80% down. You would get the same amount of days or AH of use out of both options. At the 80% discharge example you only have to charge the batteries 1/2 as often, and you need a lot less of them compared to 50% discharge. The downside would be you would lose about 10% in the number of AH you would get out of them at 80% vs 50%, which is really not bad considering the the upsides.
If you look at the lithium charts, they do lose big time in both number of cycles and total lifetime energy, when you take them deep.
The 50% rule is so pounded in to everyone's brain, it is hard to think that it may actually be incorrect.
wincrasher
Senior Member
Well, I guess I don't really understand your economics.
So lets say you want to target 220 AH of usable capacity.
So if you are going AGM, at 50%, that's 4 batteries - 4 x 110 AH= 440AH * 50%= 220 AH. Roughly $1200 in cost (Lifeline/Trojan/Etc), depending on what you get. That 288 lbs of weight and 4.89 cu ft of volume to find a place for.
@80%, then that's 2 AGMS = 2 x 110 AH =220 AH *80% = 176 AH. Less capacity, but also less weight (144 lbs) and 2.44 cu ft of volume to store. Cost of $600 +/-. You are giving up 44 AH in this scenario which could mean a full day's use of a compressor fridge.
For lithiums, you are looking at 2 batteries, but you can get higher capacity of 125 AH each = 250 AH. You can also draw down to 90%. That would be 225 AH. Cost is roughly $2400. Volume is same at 2.44 CF, but weight is only 56 lbs.
OK, that all said, let's factor in the life cycle costs based on these draw downs -
@50% SOC draw down projected 1000 cycles = $1200/1000 cycles= $1.2/ cycle.
@80% projected 500 cycles= $600/550= $1.09/cycle.
LI @ 90% = $2400/2000 = $1.2/cycle. If you accept 3000 cycles, then $0.80. Some vendors are forecasting up to 5000 cycles @80% - that would be $.48/cycle. Probably way too optimistic in my view.
If you are such a heavy user that each day is a full depletion, than you could consider these your daily costs.
So the costs are within spitting distance of each other, other than factoring in the cost to equalize the cycles lives. When you factor in the costs of multiple sets of AGMS to equal the lifespan of the Lis, then Li pulls way ahead. Also negating the benefits of the weight reduction, lesser "range anxiety" for days with weak recharging or heavy use days or the mods that could be required to find room for more than two batteries, or the inconvenience of battery pack replacements.
So in my mind, the cost of risk of hammering an AGM battery pack consistently to 20 % SOC outweighs the benefits.
So lets say you want to target 220 AH of usable capacity.
So if you are going AGM, at 50%, that's 4 batteries - 4 x 110 AH= 440AH * 50%= 220 AH. Roughly $1200 in cost (Lifeline/Trojan/Etc), depending on what you get. That 288 lbs of weight and 4.89 cu ft of volume to find a place for.
@80%, then that's 2 AGMS = 2 x 110 AH =220 AH *80% = 176 AH. Less capacity, but also less weight (144 lbs) and 2.44 cu ft of volume to store. Cost of $600 +/-. You are giving up 44 AH in this scenario which could mean a full day's use of a compressor fridge.
For lithiums, you are looking at 2 batteries, but you can get higher capacity of 125 AH each = 250 AH. You can also draw down to 90%. That would be 225 AH. Cost is roughly $2400. Volume is same at 2.44 CF, but weight is only 56 lbs.
OK, that all said, let's factor in the life cycle costs based on these draw downs -
@50% SOC draw down projected 1000 cycles = $1200/1000 cycles= $1.2/ cycle.
@80% projected 500 cycles= $600/550= $1.09/cycle.
LI @ 90% = $2400/2000 = $1.2/cycle. If you accept 3000 cycles, then $0.80. Some vendors are forecasting up to 5000 cycles @80% - that would be $.48/cycle. Probably way too optimistic in my view.
If you are such a heavy user that each day is a full depletion, than you could consider these your daily costs.
So the costs are within spitting distance of each other, other than factoring in the cost to equalize the cycles lives. When you factor in the costs of multiple sets of AGMS to equal the lifespan of the Lis, then Li pulls way ahead. Also negating the benefits of the weight reduction, lesser "range anxiety" for days with weak recharging or heavy use days or the mods that could be required to find room for more than two batteries, or the inconvenience of battery pack replacements.
So in my mind, the cost of risk of hammering an AGM battery pack consistently to 20 % SOC outweighs the benefits.
gregmchugh
Senior Member
- Joined
- Jul 22, 2012
- Posts
- 2,380
I have 220 AH AGMs under the hood on my Sprinter and if I need an average of more than 110 AH per day but less than 176 AH it makes complete sense to simply draw the batteries beyond 50% and replace the batteries more often. No need to try to lose storage space for more AGMs or to spend money on lithiums.
Yes, it costs 12% more than adding two more AGM batteries but that is not a big penalty to avoid adding two more batteries.
The "risk" of hammering AGM batteries when going beyond 50% is not real, it is a long held idea that is not backed up with data.
Yes, it costs 12% more than adding two more AGM batteries but that is not a big penalty to avoid adding two more batteries.
The "risk" of hammering AGM batteries when going beyond 50% is not real, it is a long held idea that is not backed up with data.
wincrasher
Senior Member
For the occasional minor excursion, the cost may be minimal if the data is correct about damage. In the scenario where you do it consistently, the cost is much more than 12%. The cost difference is $.49/cycle, or 45%.
Costs may be lower for lithium battery packs. This site has premade packs or give you everything you need to build one, the size you want including instructions and phone help.
<b>- 12 VOLT PACKS</b>
Even more if you build the pack yourself. <$5000 for 900AH.
<b>- 12 VOLT PACKS</b>
Even more if you build the pack yourself. <$5000 for 900AH.
wincrasher
Senior Member
Don't forget you need to add the costs of BMS if they don't include it.
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