Trickle Charge 2 12v batts in parallel question???

Hi Matt,

The problem is solvable with lead acid by having a temperature sensor that adjusts charging voltage. That's one reason I love solar. Fortunately my Magnum inverter/charger does have a temperature sensor--so I'm "good to go".

I do have a way to use a heater on my propane tanks. So far I've never had to use it.

Happy American thanksgiving.

pianotuna wrote:
Hi Matt,

I did not misquote you deliberately.

You would have a hard job designing an LI battery pack for me as I need it to be good to -40. Heating the battery bank electrically would be a zero sum game, so until someone comes up with an LI chemistry that works at -40 without the need to be warmed they will not be useful to me. Propane heating would also be futile for my particular use pattern. (i.e. 3 months storage at temperatures that rarely climb above -20 C and that are as low as -40).

From what little I know of LI, they do not trickle charge too well. That eliminates small solar as a charging source. One person on the Forums does have 1400 watt of solar powering their RV with LI batteries, so it is possible. They don't cold weather RV.

It is moot, as I'll never have the funds for an LI installation.

My ideal system would be six two volt AGM's with a capacity of 800 to 1000 amp-hours. Recharging would be met by 1250 to 1500 watts of solar.

Don,

Is true that in Regina you don't even use the snow until it is at least a year old? ;)

You do have a problem, but even Lead/Acid (be they AGM or Flooded) do not do well at low temperature. (Trust me, I have been there.) An insulated battery compartment with a provision for forced cooling is about the only hope. All batteries generate heat when they are charged, if you can use that heat to get them to a better temperature for charging, you win. But Yes, that takes charging at a rate to make heat at all.

What I am waiting for is the hybrid car batteries to start to show up on the used market. I go to a couple of electric vehicle shows a year some are hobby shows and some are trade shows. I look at prices. I too am stuck with old technology for the foreseeable future.

Matt

Hi Matt,

I did not misquote you deliberately.

You would have a hard job designing an LI battery pack for me as I need it to be good to -40. Heating the battery bank electrically would be a zero sum game, so until someone comes up with an LI chemistry that works at -40 without the need to be warmed they will not be useful to me. Propane heating would also be futile for my particular use pattern. (i.e. 3 months storage at temperatures that rarely climb above -20 C and that are as low as -40).

From what little I know of LI, they do not trickle charge too well. That eliminates small solar as a charging source. One person on the Forums does have 1400 watt of solar powering their RV with LI batteries, so it is possible. They don't cold weather RV.

It is moot, as I'll never have the funds for an LI installation.

My ideal system would be six two volt AGM's with a capacity of 800 to 1000 amp-hours. Recharging would be met by 1250 to 1500 watts of solar.

pianotuna wrote:
Hi Matt,

Six volt batteries in series would not come close to meeting my needs. One size does NOT fit all.

For example:

If an RV'er usually is on shore power, a single maintenance free battery may be the best choice for them.

If an RV'er is off the grid and deep cycles then a Lithium Ion battery bank is "as good as it gets" and is state of the art.

My 12 volt marine batteries are in two banks. One bank is 10 years old and the other is 5. They continue to more than meet my needs. I push them hard with large loads on the inverter. My ultimate battery bank would not be LI as I RV in -30 temperatures. I'd love to have six large two volt cells totaling 800 amp-hours, but can not afford the remodeling that would be required. Nor can I afford the cost of the cells.

Three different needs for three different RV styles.

Piano,

I really do hate being mis-quoted - intentionally.

The response was to Mountain's specific question with experience based on 60 years a waterman, 40 years as a licensed ship's engineer and several engineering degrees. I did run a very successful business while the owners in this area still had money for discretionary spending. That is over and I retired.

There never was or will be one size does not fit every application, but a recommendation that an owner cannot afford will get very little appreciation.

For what Mountain is doing (from the little we know) a pair of good golf cart batteries is the bag for the buck and unlike paralleled 12Vs, there is much less chance of a battery explosion.

And, if you have the money for LiPos, do not go for high AH. Do what the Hybrid Cars are doing (for a reason). If you have the money to go that way, I will design you high voltage bank with a high efficiency direct inverter and you can abandon your old copper heavy 12V stuff.

Yes, I have done the above, but the first was so long ago that we had to use 10ea grp 27s as a main bank.

Matt - going back to what I was doing.

Please listen to what pianotuna is saying, especially about connecting the charging cables.

I used to have a boat and had 6-volt batteries in series for my house bank and 12-volt batteries in parallel for my starting bank. Worked great but for RVing I lean more towards 12-volt deep cycle batteries, instead of 6-volt batteries in series. The reason is because if you have 2 6-volt batteries in series and one cell goes bad, then you have nothing. But if you have 2 12-volt batteries in parallel and one goes bad, you still have one good battery to limp along on.

Tim

Hi Matt,

Six volt batteries in series would not come close to meeting my needs. One size does NOT fit all.

For example:

If an RV'er usually is on shore power, a single maintenance free battery may be the best choice for them.

If an RV'er is off the grid and deep cycles then a Lithium Ion battery bank is "as good as it gets" and is state of the art.

My 12 volt marine batteries are in two banks. One bank is 10 years old and the other is 5. They continue to more than meet my needs. I push them hard with large loads on the inverter. My ultimate battery bank would not be LI as I RV in -30 temperatures. I'd love to have six large two volt cells totaling 800 amp-hours, but can not afford the remodeling that would be required. Nor can I afford the cost of the cells.

Three different needs for three different RV styles.

Actually Mountain,
As long as you connect positive to positive and negative to negative it will all work as well as it can. At solar trickle charger currents, balancing is just not an issue.

But, no matter what you do, expect that one battery will end up not being as well charged as the other. This is a fact of lead-acid batteries in parallel. Use them as long as you can, and then proceed to do the 6V in series.

Batteries charged in parallel has always been a bad idea. This is just the sort of thing that I did for a lot of performance cruisers (read retired racing keel boats) before the depression.

Matt

Batteries in parallel act as one big battery.

I leave my battery in place and use the OEM battery disconnect switch, and turn the Converter circuit breaker off. I use a Battery Minder to keep the battery charged.

Even if the batteries will not be removed from the TT, I recommend disconnecting them from the trailer main supply/distribution.

For trickle chargeing it does not matter you can hook both to the same battery or positive to one and negative to the other (and it does not matter which one if they are in parallel) your choice.

one word of caution,, Solar panels come in two types.. Some have built in reverse current blockers (Diodes) some do not, if yours does not then it charges by day and DISCHARGES by night.