12v marine battery in series with 12v deep cycle

[almac]

have 4 x 12v batteries 2 x 12v 135rc marine batteries in parallel. ( i think these are about 80ah each) 2 x 12v 100ah deep cycle in parallel. these 2 sets in series to make 24v 160ah bank. i have noticed at the end of each day the marine batteries are nearly full with SG of just above 1.250. the deep cycle are at about 75% SG 1.225. both sets iv been charging at the end of the day on separate 12v chargers till both have SG approx 1.250 or better. then using them as a 24v bank for the next 24hrs connected to the CC on a 24v charge during the day. why are the deep cycle discharging more than the marine? or is the marine charging faster of the CC during the day? the deep cycle suck 20amps when i put them on the dc charger off the gen. while the marine go straight to absorb then full in an hour or so

[Mike90250]

Ah ! you have discovered the special secret of mixing batteries. Unless they are from the same batch at the factory, they are mismatched. There is no cure. Mixing old with new, eventually fails faster then if they were all old to start with. The best battery hogs the load, and soon ages to match the others, then the next strongest starts the race to the bottom again.

To recharge the weaker batteries, you have to pull them from the bank, or use an isolated charger on only the weak ones.

[Sunking]

Say goodbye to your deep cycle batteries in a very short time, soon followed by your Marine batteries. You cannot mix batteries of age, size, different models, or manufactures. They should all be matched up . just like your solar system have to be matched up to your batteries and daily power requirement. If you if you continue your batteries will soon be boat anchors.

When that happens bury them in Epsom Salts, then buy yourself a new matched set sized correctly for that Free Sun Energy.

[inetdog]

Putting mismatched batteries in parallel is bad enough, since you cannot force even load and charge distribution.
But putting mismatched batteries in series is even worse.
If they are not the same AH capacity you will have to keep the lowest level of discharge above the your design threshold value of the smallest battery. And any voltage based monitoring will not be particularly useful (even for LVDC) unless you measure the voltage of each battery.
And finally, the different batteries will have different Peukert coefficients, different self-discharge and different coulombetric efficiency (the ratio of charge replaced to charge removed to keep the same SOC.
Do not do it.

[almac]

Ah ! you have discovered the special secret of mixing batteries. Unless they are from the same batch at the factory, they are mismatched. There is no cure. Mixing old with new, eventually fails faster then if they were all old to start with. The best battery hogs the load, and soon ages to match the others, then the next strongest starts the race to the bottom again.

To recharge the weaker batteries, you have to pull them from the bank, or use an isolated charger on only the weak ones.

thanks for the replies. at the moment i am pulling them out of the bank at the end of each day and charging them on separate 12v chargers till all have SG 1.250 or better. been reading the stickies and understand differences in internal resistance and diagonal wiring in parallel. still working with what i have , think i might expand bank with marine batteries since they have lower internal resistance and can charge/discharge faster. am thinking of expanding to 400ah 24v bank with marine batteries and using a 40amp charger off the gen for now. will expand solar to charge that bank later

[Sunking]

think i might expand bank with marine batteries since they have lower internal resistance and can charge/discharge faster.

You do understand by doing that you are sacrificing cycle life and thus just about doubling your battery cost with Hybrids right?

Unless you have a need for Hybrids or AGM, it makes no economic sense to use them. You would just double the cost of your free energy. Instead of paying 50 to 75-cents per Kwh, you double that. With AGM 4 times higher than FLA Deep Cycle. Be careful what you ask for. Your education and learning is getting real expensive and much higher than it need be.

[almac]

You do understand by doing that you are sacrificing cycle life and thus just about doubling your battery cost with Hybrids right?

Unless you have a need for Hybrids or AGM, it makes no economic sense to use them. You would just double the cost of your free energy. Instead of paying 50 to 75-cents per Kwh, you double that. With AGM 4 times higher than FLA Deep Cycle. Be careful what you ask for. Your education and learning is getting real expensive and much higher than it need be.

actually the marine batteries are cheaper than the deep cycle. at present im not discharging below 75% per day with a 160ah bank . im only using laptops tv a couple of lights and the coffee machine, blender for a couple of mins, some days the washing machine. an electric chainsaw for 5mins, only in the winter. thats why i thought the marine would be better because i use high discharges for short bursts, like the coffee machine.

[lkruper]

actually the marine batteries are cheaper than the deep cycle. at present im not discharging below 75% per day with a 160ah bank . im only using laptops tv a couple of lights and the coffee machine, blender for a couple of mins, some days the washing machine. an electric chainsaw for 5mins, only in the winter. thats why i thought the marine would be better because i use high discharges for short bursts, like the coffee machine.

Does it take you the same amount of time to start your car as it does to make a pot of coffee

[inetdog]

Does it take you the same amount of time to start your car as it does to make a pot of coffee

"Well, the car is really hard to start...."

[Sunking]

"Well, the car is really hard to start...."

That would be a Fricken Old Rebuilt Dodge right?

[almac]

"Well, the car is really hard to start...."

takes about 2mins on a 50amp discharge to make a coffee. a discharge rate of c/3 on a 160ah battery bank, i think in one of SKs stickies a discharge of c/3 is fine for marine batteries, given im discharging bank to about 75% per day now a 160ah bank is big enough. dont need to do any more other than match the batteries. 750w panels pwm cc delivering about 400w is the right size for a 160ah bank, been thinking about why the deep cycle battery set is more discharged at days end than the marine set. would it be the marine set is sucking up more charging amps reaching full charge 1st. so denying the deep cycle charging current? or does current flow evenly through a series battery bank

here is a pic of my 3 x250w panels midday sun winter. they get 8hrs full sun in winter. from 10 till 2pm they produce 700w. it is 33 deg south here just north if sydney. DSCN7728.JPG

decided to separate these batteries and charge / discharge them separately. so the coffee machine will draw 50amps from the marine batteries now at 80ah. so it will be a c/1.5 discharge. is ok?
DSCN7729.JPG

[SunEagle]

takes about 2mins on a 50amp discharge to make a coffee. a discharge rate of c/3 on a 160ah battery bank, i think in one of SKs stickies a discharge of c/3 is fine for marine batteries, given im discharging bank to about 75% per day now a 160ah bank is big enough. dont need to do any more other than match the batteries. 750w panels pwm cc delivering about 400w is the right size for a 160ah bank, been thinking about why the deep cycle battery set is more discharged at days end than the marine set. would it be the marine set is sucking up more charging amps reaching full charge 1st. so denying the deep cycle charging current? or does current flow evenly through a series battery bank

here is a pic of my 3 x250w panels midday sun winter. they get 8hrs full sun in winter. from 10 till 2pm they produce 700w. it is 33 deg south here just north if sydney. [ATTACH]6986[/ATTACH]

decided to separate these batteries and charge / discharge them separately. so the coffee machine will draw 50amps from the marine batteries now at 80ah. so it will be a c/1.5 discharge. is ok?
[ATTACH]6987[/ATTACH]

A C/1.5 discharge is too fast for FLA batteries. They will not last very long.

[Bala]

A C/1.5 discharge is too fast for FLA batteries. They will not last very long.

The new batteries are probably just a cheap start battery with a marine 4x4 sticker on the. I would not use them in my boat or 4x4.

They will die quickly with this kind of discharge and load.

[Mike90250]

InverterPowerLog_6-8-2015am3250watts.jpgThis is today's microwave and toaster run (on a large 800ah 48V system) it beats on it pretty hard!

[SunEagle]

This is today's microwave and toaster run (on a large 800ah 48V system) it beats on it pretty hard!
[ATTACH]6995[/ATTACH]

Thanks for the vivid picture Mike.

Microwaves and a battery power source is not a good combination.