Lithium Batteries?? VS dual 6 volts

[John in Santa Cruz]

there's two ways to wire 4 6V batts to get 12V... both deliver the same capacity, and have the same features described in the above post.

method one, connect battery 1 and batt 2 in series, connect batt 3 and 4 in series, then connect these 2 pairs in parallel.

method two is to connect 1 and 2 in parallel, 3 & 4 in parallel, then connect these two pairs in series. this better equalizes the load on each battery, and is whats shown in the diagram I posted above. also carefully note which terminals are connected to the load, and in series, this equalizes the total wire resistance as seen by each battery, which further equalizes the load on all 4.

[fudge_brownie]

I can see the value of four batteries. My question is, what happens when after two years of use, one the batteries fails? Can just one battery be replaced? I know in parallel installations the batteries need to be identical. Does that mean identical in model or does it also include the age and charge capabilities?

[alanmalk]

Originally Posted by fudge_brownie

I can see the value of four batteries. My question is, what happens when after two years of use, one the batteries fails? Can just one battery be replaced? I know in parallel installations the batteries need to be identical. Does that mean identical in model or does it also include the age and charge capabilities?

All parameters should be identical, otherwise the risk is that a weaker battery could discharge a stronger battery. If one fails - that is a worst case scenario. It could conceivably pull down the other battery to zero and cause it to fail also.
--
Alan

[John in Santa Cruz]

as batteries age with use, their AH capacity goes down. to replace one of a parallel pair with a new battery would leave unmatched batteries, the older one would drag the newer one down some.

I've never had a decent quality battery totally fail, just wear out and stop holding sufficient charge to be useful. Its pretty much physically impossible for a lead acid 3-cell battery to become a short, more likely one or more cells sulfate, and in that case ALL the batteries in the stack are in similar condition, OR the other possible failure mode is a break in the internal connections between cells, causing the battery to become open circuit.

[Brian B-P]

Originally Posted by fudge_brownie

I can see the value of four batteries. My question is, what happens when after two years of use, one the batteries fails? Can just one battery be replaced? I know in parallel installations the batteries need to be identical. Does that mean identical in model or does it also include the age and charge capabilities?

Batteries used together in both parallel and series combinations should behave identically - that means the same capacity and internal resistance (which change with age), but in practice most people just buy identical batteries at the same time and replace them together. The matching is much more important in the series connection case than in parallel.

• If parallel batteries are not the same, they take and deliver unequal current when charging and discharging at the same voltage.
  • That can be okay, but one will wear out first, and when they sit idle the more-charged one will transfer current to the less-charged one, which is inefficient.
  • Matching parallel batteries improves the efficiency of the system.
  • Everyone who connects a trailer to the charge line of the tow vehicle is operating mis-matched batteries in parallel as long as the connection is active - that's okay.
• If series-connected batteries are not the same, they get out of balance as one gets more charged and discharged than the other with the same current.
  • This can be addressed to some extent by re-balancing them, which means charging them separately (so with a 6-volt charger in this case) to the same state and then using them again.
  • If series-connected batteries get out of balance far enough, the less-charged one can be ruined by excessive discharge; rebalancing by separate charging can avoid that.

[Losmuertos21]

Hi. What brand of 6v batteries do you recommend? Thanks.

[John in Santa Cruz]

Originally Posted by Losmuertos21

Hi. What brand of 6v batteries do you recommend? Thanks.

Trojan is the gold standard in flooded golf cart batteries (and most any other deep cycle lead-acid). The standard golf cart size that Escape uses on their dual 6V systems is the GC-2, Trojan's standard GC-2 battery is the T-105, they also have a T-125 with extended capacity (240AH vs 225AH, both are 20 hour capacities).

[Upfisk]

Originally Posted by Losmuertos21

Hi. What brand of 6v batteries do you recommend? Thanks.

We live in a solar powered house, it ran on 16 Crown 6 volt 395 amp hour batteries for 5 years, they eventually wore out. Crown batteries are the battery of choice for off grid solar installations in AZ. Currently we are running AGM batteries, 24-2 V, at 1400 amp hrs each in our house. We have a 48 V inverter.

Our problem with Trogan betteries is in the 14 years we had our sailboat in the Caribbean, we bought Trogan batteries twice. They came presulfated so we did not have to age them. Sulfation occurs in batteries during long periods of storage or age of the battery. Trogan was selling old batteries in the Caribbean and keeping fresh stock in the US. Check the manufacture date on a battery before buying it. We have seen 6-9 month old golf cart batteries in stores.

[fudge_brownie]

I switched from the original Interstate 6 volt to AGM from Crown. No more false alarms. They do not off gas as they are sealed.

[Perry Butler]

Originally Posted by John in Santa Cruz

I've never had a decent quality battery totally fail, just wear out and stop holding sufficient charge to be useful. Its pretty much physically impossible for a lead acid 3-cell battery to become a short, more likely one or more cells sulfate, and in that case ALL the batteries in the stack are in similar condition, OR the other possible failure mode is a break in the internal connections between cells, causing the battery to become open circuit.

Ours was a short. After about 50 nights of camping our Crown AGM's failed. Contacted the wrong representative from Crown (he was fired after our problem, but that's another story), so it took at least 20 nights to what should have taken one or two additional nights. We could charge the AGM's up to 13.8 (two hours after a charge) at the Organ Pipe NP office using a smart charger I always carry. At 1 pm the charge read 12.2, but at 4 am 11.4 and progressively worse the more evenings we used the batteries. The last time they failed around 10.2. We had six cold, cold nights at Organ Pipe. Luckily we never burnt out the fridge, or furnace. Once in Lost Dutchman, after requesting another Crown rep and answering many questions, Crown had two new AGM's shipped to Phoenix and both batteries were replaced. Our failed batteries were immediately put on a pallet and shipped back to Crown.

During those 20 nights we purchased a new 12v marine battery from Costco and ordered a Victron 712 BMV.

The CEO of manufacturing talked to me a couple of times. They'd never had this type of failure (yea, right!), but after all they did have the batteries shipped back to them to be broken down for inspection. The last time he called they had found a scrub mark on one corner of the battery case bottom. They asked if I'd ever dropped the battery. I hadn't. When they cut the battery apart they saw deformation consistent with a dropped battery. He explained the problem, but at that point I really didn't care, so don't remember the details.

When I was looking for answers in Mesa, before buying a battery at Costco, I stopped at a huge Trojan dealer (70% sales for golf carts) and asked for help. He said their failure rate on flooded was <10% but much less for AGM's, with lack of needed maintenance for flooded being the main culprit. No matter what vendor there will always be failures somewhere. This is a fact of life. He also said they are recommending AGM's over flooded for golf carts.

All batteries can fail early, and all will fail eventually. I have two smart battery chargers with the 20a Charge It stored underneath the back bench, and a NOCO Genius in our garage stall.

Enjoy,

Perry