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Charge 2 x 6V on 12V Charger

Started by Olin Frank December 18, 2011
If I have two 6V SLA's of the same brand, capacity, and past usage,
can I safely series wire them to charge with my existing 12V charger?

Olin Frank
On Dec 18, 1:02=A0pm, olinfr...@etherwax.com (Olin Frank) wrote:
> If I have two 6V SLA's of the same brand, capacity, and past usage, > can I safely series wire them to charge with my existing 12V charger? > > Olin Frank
Yep. Thats exactly what a 12v SLA is. NT
NT wrote:
> On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: >> If I have two 6V SLA's of the same brand, capacity, and past usage, >> can I safely series wire them to charge with my existing 12V charger? >> >> Olin Frank > > Yep. Thats exactly what a 12v SLA is.
If they are at the same state-of-charge when you start, yes. Otherwise, the battery that has the lower open circuit voltage might be damaged. You'd be much better off using a 6 V SLA charger and putting the batteries in parallel, because each battery would be less likely damaged through cell reversal. --Winston
"Winston = Wanker "
Olin Frank
>> >>> If I have two 6V SLA's of the same brand, capacity, and past usage, >>> can I safely series wire them to charge with my existing 12V charger? >>> >>> Olin Frank >> >> Yep. Thats exactly what a 12v SLA is. > > If they are at the same state-of-charge when you start, yes. > Otherwise, the battery that has the lower open circuit > voltage might be damaged.
** Err - the other way around fuckhead.
> You'd be much better off using a 6 V SLA charger and > putting the batteries in parallel,
** Advised against by all battery makers.
> because each battery > would be less likely damaged through cell reversal.
** Completely nuts. Cell ( voltage) reversal can only happen during discharge. ... Phil
Olin Frank wrote:
> If I have two 6V SLA's of the same brand, capacity, and past usage, > can I safely series wire them to charge with my existing 12V charger? > > Olin Frank
Aie-Yup! Jess more 2V cells in series, son..
Winston wrote:
> NT wrote: >> On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: >>> If I have two 6V SLA's of the same brand, capacity, and past usage, >>> can I safely series wire them to charge with my existing 12V charger? >>> >>> Olin Frank >> >> Yep. Thats exactly what a 12v SLA is. > > If they are at the same state-of-charge when you start, yes. > Otherwise, the battery that has the lower open circuit > voltage might be damaged. > > You'd be much better off using a 6 V SLA charger and > putting the batteries in parallel, because each battery > would be less likely damaged through cell reversal. > > --Winston >
Not quite correct; the statement is _close_ when mentioning a cell in that series connection. Excess charging current (the stupidity of a fast charge) candamage any battery (one or moer cells). Nominal charging current will not do any damage (stated is the two batteries are in same/similar condition).
On Dec 19, 5:55=A0am, Winston <Wins...@BigBrother.net> wrote:
> NT wrote: > > On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: > >> If I have two 6V SLA's of the same brand, capacity, and past usage, > >> can I safely series wire them to charge with my existing 12V charger? > > >> Olin Frank > > > Yep. Thats exactly what a 12v SLA is. > > If they are at the same state-of-charge when you start, yes. > Otherwise, the battery that has the lower open circuit > voltage might be damaged.
damaged, no.
> You'd be much better off using a 6 V SLA charger and > putting the batteries in parallel, because each battery > would be less likely damaged through cell reversal. > > --Winston
Charging cells in series does not cause any cell to see reverse voltage. Ever. Connecting lead acids in parallel can cause serious problems, both to the battery and to the nearby user, and is never recommended. NT
NT wrote:
> On Dec 19, 5:55 am, Winston<Wins...@BigBrother.net> wrote: >> NT wrote: >>> On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: >>>> If I have two 6V SLA's of the same brand, capacity, and past usage, >>>> can I safely series wire them to charge with my existing 12V charger? >> >>>> Olin Frank >> >>> Yep. Thats exactly what a 12v SLA is. >> >> If they are at the same state-of-charge when you start, yes. >> Otherwise, the battery that has the lower open circuit >> voltage might be damaged. > > damaged, no.
Two 6 V SLAs. One is charged to nearly 100% or say 6.3 V. We place it in series with one that is charged to about 35% or say 6.05 V At 10 A discharge we can think of the top battery as a resistor measuring 0.63 ohm and the bottom battery equivalent to a 0.60 ohm resistor. The top battery will have 51% of the charge voltage across it and the bottom battery will have only 49%. If we begin charging them at say 10 A, the battery charged to nearly 100% will get about 3 W more charge power than the relatively discharged battery. Successive charge and discharge cycles will cause the difference in state - of - charge to widen until eventually, the bottom battery sulfates and fails. That's why we never add acid to individual cells of a conventional wet cell battery. It causes an analogous imbalance which can result in the failure of the battery, if it cannot be equalized. --Winston
>> You'd be much better off using a 6 V SLA charger and >> putting the batteries in parallel, because each battery >> would be less likely damaged through cell reversal. >> >> --Winston > > Charging cells in series does not cause any cell to see reverse > voltage. Ever.
Reverse voltage can happen on discharge, not charge.
> Connecting lead acids in parallel can cause serious > problems, both to the battery and to the nearby user, and is never > recommended.
One can equalize the charge between them and connect them in parallel safely. Many diesel - powered cars had two 12 V batteries in parallel, for example. Here, we see three batteries in parallel for trailer use: http://www.etrailer.com/Merchant2/graphics/00000001/pics/q/u/qu22749_800.jpg --Winston
On Dec 19, 4:39=A0pm, Winston <Wins...@BigBrother.net> wrote:
> NT wrote: > > On Dec 19, 5:55 am, Winston<Wins...@BigBrother.net> =A0wrote: > >> NT wrote: > >>> On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: > >>>> If I have two 6V SLA's of the same brand, capacity, and past usage, > >>>> can I safely series wire them to charge with my existing 12V charger=
?
> > >>>> Olin Frank > > >>> Yep. Thats exactly what a 12v SLA is. > > >> If they are at the same state-of-charge when you start, yes. > >> Otherwise, the battery that has the lower open circuit > >> voltage might be damaged. > > > damaged, no. > > Two 6 V SLAs. > > One is charged to nearly 100% or say 6.3 V. > We place it in series with one that is charged > to about 35% or say 6.05 V > > At 10 A discharge we can think of the top battery as > a resistor measuring 0.63 ohm and the bottom > battery equivalent to a 0.60 ohm resistor.
We've no idea what the OP's discharge conditions are
> The top battery will have 51% of the charge voltage > across it and the bottom battery will have only 49%. > > If we begin charging them at say 10 A, the battery > charged to nearly 100% will get about 3 W more > charge power than the relatively discharged battery.
Pdiss is usually a non-issue
> Successive charge and discharge cycles will > cause the difference in state - of - charge > to widen until eventually, the bottom battery > sulfates and fails.
no, when the fuller cells are fully charged, further current only charges the less charged ones. Charging equalises.
> That's why we never add acid to individual > cells of a conventional wet cell battery. > It causes an analogous imbalance which can result > in the failure of the battery, if it cannot > be equalized. > > --Winston > > >> You'd be much better off using a 6 V SLA charger and > >> putting the batteries in parallel, because each battery > >> would be less likely damaged through cell reversal. > > >> --Winston > > > Charging cells in series does not cause any cell to see reverse > > voltage. Ever. > > Reverse voltage can happen on discharge, not charge.
> > Connecting lead acids in parallel can cause serious > > problems, both to the battery and to the nearby user, and is never > > recommended. > > One can equalize the charge between them and connect > them in parallel safely. =A0Many diesel - powered cars had > two 12 V batteries in parallel, for example. > > Here, we see three batteries in parallel for trailer use: > > http://www.etrailer.com/Merchant2/graphics/00000001/pics/q/u/qu22749_...
Sure, but its not appropriate advice for someone that is discharging them separately, and doesnt even know whether they can be connected in series or not. NT
Winston wrote:
> NT wrote: > >> On Dec 19, 5:55 am, Winston<Wins...@BigBrother.net> wrote: >> >>> NT wrote: >>> >>>> On Dec 18, 1:02 pm, olinfr...@etherwax.com (Olin Frank) wrote: >>>> >>>>> If I have two 6V SLA's of the same brand, capacity, and past usage, >>>>> can I safely series wire them to charge with my existing 12V charger? >>> >>> >>>>> Olin Frank >>> >>> >>>> Yep. Thats exactly what a 12v SLA is. >>> >>> >>> If they are at the same state-of-charge when you start, yes. >>> Otherwise, the battery that has the lower open circuit >>> voltage might be damaged. >> >> >> damaged, no. > > > Two 6 V SLAs. > > One is charged to nearly 100% or say 6.3 V. > We place it in series with one that is charged > to about 35% or say 6.05 V > > At 10 A discharge we can think of the top battery as > a resistor measuring 0.63 ohm and the bottom > battery equivalent to a 0.60 ohm resistor. > > The top battery will have 51% of the charge voltage > across it and the bottom battery will have only 49%. > > If we begin charging them at say 10 A, the battery > charged to nearly 100% will get about 3 W more > charge power than the relatively discharged battery.
No it won't. The battery that is discharged the most gets the most charge power.The lower the charge on a battery, the higher its internal resistance. The .63 ohm equivalent top battery will receive higher power than the .60 ohm equivalent bottom battery. P = I^2 * R, so the top battery gets more. Seems moot anyway, as the op specified batteries of the same brand, capacity and usage. If one wants to discuss batteries of different usage/discharge level/specs/whatever, then it is best to independently charge, where the charge can be tailored to the individual battery. Ed
> > Successive charge and discharge cycles will > cause the difference in state - of - charge > to widen until eventually, the bottom battery > sulfates and fails. > > That's why we never add acid to individual > cells of a conventional wet cell battery. > It causes an analogous imbalance which can result > in the failure of the battery, if it cannot > be equalized. > > --Winston > > >>> You'd be much better off using a 6 V SLA charger and >>> putting the batteries in parallel, because each battery >>> would be less likely damaged through cell reversal. >>> >>> --Winston >> >> >> Charging cells in series does not cause any cell to see reverse >> voltage. Ever. > > > Reverse voltage can happen on discharge, not charge. > >> Connecting lead acids in parallel can cause serious >> problems, both to the battery and to the nearby user, and is never >> recommended. > > > One can equalize the charge between them and connect > them in parallel safely. Many diesel - powered cars had > two 12 V batteries in parallel, for example. > > Here, we see three batteries in parallel for trailer use: > > http://www.etrailer.com/Merchant2/graphics/00000001/pics/q/u/qu22749_800.jpg > > > --Winston