Firefly Oasis carbon foam AGM battery
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shade
Well-known member
I know they aren't starting batteries, but what kind of cold cranking amps would a good 12V Golf Cart battery deliver?
A good 12V GC battery is a pair of 6V ones.
For good deep cycling performance, the cheapest I would buy is a pair of Duracell (actually Deka/East Penn) FLA, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.
GC2 = 215AH Deka Pro-Master GC10
EGC2 = 230AH aka GC15
Maybe EPM lists CCA, but IMO irrelevant, because it is more than enough to get you going as a Starter, won't break a sweat trivial ask for any deep cycle once you get up to that sort of Ah capacity.
Same with Trojan, Crown, Superior, US Battery and of course Rolls/Surrette, can't go wrong with any of them, but those will cost you more
shade
Well-known member
Sure, but then there's no way to isolate one from another, so if one fails, the entire 12V system goes down.
Do you think 6V GC batteries are reliable enough that the redundancy of having 2x12V batteries offers little benefit?
Are these really the only batteries on board? You're running House loads off your one and only Starter?
Carry a pocket lithium jumpstarter powerpak in the glovebox, keep it topped up and don't use it to run screen gadgets.
Yes, paralleled strings are best avoided, certainly to be minimized.
A decent bank properly cared for and monitored should not yield any surprises, you will want to replace it long before there's any chance of a catastrophic failure.
Carry a pocket lithium jumpstarter powerpak in the glovebox, keep it topped up and don't use it to run screen gadgets.
Yes, paralleled strings are best avoided, certainly to be minimized.
A decent bank properly cared for and monitored should not yield any surprises, you will want to replace it long before there's any chance of a catastrophic failure.
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shade
Well-known member
Yes, really.
I have a single G31 AGM battery on board, and a commercial AGM jump pack. The only significant load is an Indel B fridge, and it only needs to run overnight before a lengthy engine run recharges it the next day. I'm adding a house battery & solar charging to allow more unattended time away from the truck.
A fridge is a big load.
It takes lead a minimum 6 hours to get to Full no matter how many amps available in bulk stage.
Thus, prioritize solar unless driving 8-hour stints daily.
But PSOC half the cycles, only getting to Full the other half - as per endAmps - is better than most.
Ideally match Starter and House in that scenario, use an adjustable LVC rather than stock ACR.
The two act as a single bank as long as SoC remains well above what's needed for the Starter half to crank.
The LVC isolates Starter at that point, all House loads carried by House half only from then on, try to get both recharged ASAP.
Yes wear will be a bit uneven, especially if you take House down to 60% DoD or lower.
So swap them around monthly. If Lifeline, can equalize at that time as well.
This setup is not nearly as good as a dedicated Starter and say 400Ah of House bank, but makes the most use of limited resources.
It takes lead a minimum 6 hours to get to Full no matter how many amps available in bulk stage.
Thus, prioritize solar unless driving 8-hour stints daily.
But PSOC half the cycles, only getting to Full the other half - as per endAmps - is better than most.
Ideally match Starter and House in that scenario, use an adjustable LVC rather than stock ACR.
The two act as a single bank as long as SoC remains well above what's needed for the Starter half to crank.
The LVC isolates Starter at that point, all House loads carried by House half only from then on, try to get both recharged ASAP.
Yes wear will be a bit uneven, especially if you take House down to 60% DoD or lower.
So swap them around monthly. If Lifeline, can equalize at that time as well.
This setup is not nearly as good as a dedicated Starter and say 400Ah of House bank, but makes the most use of limited resources.
shade
Well-known member
All worth consideration. The CTEK system I have functions as you described WRT charging behaviour between House & Start.
Before summer is out, I need to conduct a true test of the power consumption of my fridge in hot conditions over 24 hours so I have more than an educated guess to work with.
I'd have to dedicate far more weight for a 400Ah SLA House bank than I'm willing to spare. Before going that route, I'd more likely use a 200Ah LFP House bank, installed in an under-the-truck bed tray. I know PSoC favours LFP, so that might be worth doing, along with enough solar capacity to keep it going for 5-7 days. That's about as long as I can see backpacking away from the truck without resupply, at least if I was taking a trip where I left the fridge running in my absence.
Again, I need some real numbers to determine power consumption to figure that out properly. I'd hoped that Firefly batteries might be around the cost of LFP, but unsurprisingly, there's no free lunch at the battery counter.
I'm referring to time spent parked while I'm out hiking etc. Otherwise I need to consider the battery going flat after a day or two parked.
I did manage to get three days out of my G31 AGM battery and the fridge during warm weather in Canyonlands NP, but I knew I was pushing the limit. It also wasn't really hot weather, and I was able to leave the truck cab windows down, with a DIY Reflectix boot over the fridge. I'm amazed that manufactured fridge covers are usually black.
OK, was thinking maybe the need to remove portable powerpaks for use away from the mothership, like electric powered dinghies or eBikes.
Also some have camping trailers, plus separate House banks in the TV.
All of which can be designed around but get more complicated.
I met one van dweller rotated 3kWh LFP packs into coffee shops with a charging rig in their backpack, pretending to just be a typical laptop warrior.
Had to dial down the current to start, then slowly increase until they saw voltage start to drop, sometimes, the lights dim or they actually tripped a fuse.
I tried to convince them they should figure out how to tap into EV chargers instead, but they felt that would add too much to the cost.
Also some have camping trailers, plus separate House banks in the TV.
All of which can be designed around but get more complicated.
I met one van dweller rotated 3kWh LFP packs into coffee shops with a charging rig in their backpack, pretending to just be a typical laptop warrior.
Had to dial down the current to start, then slowly increase until they saw voltage start to drop, sometimes, the lights dim or they actually tripped a fuse.
I tried to convince them they should figure out how to tap into EV chargers instead, but they felt that would add too much to the cost.
Alloy
Well-known member
Instead of following the economical method of calculating loads I choose to fill the available roof space with as much solar that could be easily installed. It is one of the best things I did as power use and charging is no longer a concern.
For 3 weeks we've been averaging 60-100Ah of use per day with just solar charging. To save propane some days are (+100Ah) more when 8cuft fridge is on 110VAC through the inverter. With the exception of 1 or 2 days the solar charging was in float before evening.
Right now (1:00pm) at site in the trees the Panasonic panels (covered in dust after being off road, with no rain and with 30% shade) are producing 45% of the rated output.
FYI....our fridge uses less power when it is full than it does when it is say less than 80% full. When it is full there is less air movement past the evaporator and the internal (tested) temp next to the walls is too warm.
For 3 weeks we've been averaging 60-100Ah of use per day with just solar charging. To save propane some days are (+100Ah) more when 8cuft fridge is on 110VAC through the inverter. With the exception of 1 or 2 days the solar charging was in float before evening.
Right now (1:00pm) at site in the trees the Panasonic panels (covered in dust after being off road, with no rain and with 30% shade) are producing 45% of the rated output.
FYI....our fridge uses less power when it is full than it does when it is say less than 80% full. When it is full there is less air movement past the evaporator and the internal (tested) temp next to the walls is too warm.
shade
Well-known member
Talk about dirtbag living! That's pretty bold, bringing you batteries in like that. I hope he tipped well.
I may eventually make a 50Ah LFP battery box, but my main concern is fixed power on the truck. I prefer not to tow when I travel.
Speaking of which, I hate U-Haul, and I added another reason to the list this morning. Smug moron bastidges.
This isn't my truck, but I have the same camper. I hadn't considered covering it with panels, but that wouldn't interfere with using crossbars for carrying boats, and panels are cheaper than LFP batteries. I could also run higher voltages with more/bigger panels. The camper's perimeter frame has T-slots, so installation shouldn't be difficult. Pointing the truck south and opening it up would probably be about optimal.
I already have a 100W Renogy panel I may use as a wind deflector on the roof of the truck cab. I'd make that one detachable so I could move it to the light, if needed. I'll test my fridge with a fully cooled, standard assortment of food & beverages.
This is turning more into an electrical design thread for my truck. I'd planned on starting one next week, but this is going pretty well already.
What retailer has a good assortment of panel sizes?
luthj
Engineer In Residence
I like to start on Amazon, then when I get a size thats workable, I shop for the best deals. Since there is a finite number of cell sizes, you are basically limited by total cell count, and the number of rows.
I would suggest one large high voltage panel if it fits. Avoid flexible panels if you can, they are lighter, but not as durable. I find the larger panels have less frame weight. Some have very thick glass though, which makes them heavy...
200W should handle a fridge without issue.
I would suggest one large high voltage panel if it fits. Avoid flexible panels if you can, they are lighter, but not as durable. I find the larger panels have less frame weight. Some have very thick glass though, which makes them heavy...
200W should handle a fridge without issue.
shade
Well-known member
Thanks. I want a rigid panel. I'm not sure how well a flexible panel would stick to my camper top, but I don't want to deal with the short lifespan anyway.
I'll look at the 200W-300W range. A single panel would simplify things, so I'll try for that.
I'm also considering using resistance heat to get 2.5 gallons of water up to shower temperature, but I'd only do that occasionally, and with the alternator turning. I have a small Cornelius keg already in use for that, but I heat it with propane or a camp fire. Dropping a DC immersion heater into it would be much simpler. That's a more distant project, though.
I'll look at the 200W-300W range. A single panel would simplify things, so I'll try for that.
I'm also considering using resistance heat to get 2.5 gallons of water up to shower temperature, but I'd only do that occasionally, and with the alternator turning. I have a small Cornelius keg already in use for that, but I heat it with propane or a camp fire. Dropping a DC immersion heater into it would be much simpler. That's a more distant project, though.
