I have read repeatedly here how you need a hydrometer if you want to really know the SOC of a battery. This was clearly confirmed with the results I got...Battery is a new, never used Interstate group 24 12v marine battery. I've had it for several months now and it's just been sitting in my garage on the Battery Tender. The date code shows it to be almost a year old though, so I'm sure it was somewhat discharged before I got it. Anyway, I disconnected it from the tender and waited about 24 hours before testing. All 6 cells were pretty close to each other, but the SG was only 1.225 to 1.250. If I understand correctly, fully charged they should read 1.275. I don't understand why the battery wouldn't be fully charged since I had it connected to the tender. I can't imagine it would be sulfated since it's never been used, but what explains the low SG?Hydrometer is a EZ Red 101.

You might have stratification, where the watery part is on top giving low readings. The high acid at the bottom eats the bottom of the plates-not good) Try to keep the mix even.With the caps on, tip the battery up on its end and leave it for five minutes, then tip it up on the other end and wait five minutes, then when it is upright, wobble it back and forth some. Now take the SGs again.To prevent stratification while on Float, you need to give the battery a shot of higher voltage every so often.

Those readings are fairly close to full charge. Did you add any water the day before you read them? That can have a negative effect. They should be charged before you water them and again after.Here's more info:Battery infoHope this helps.

BFL13 wrote:You might have stratification, where the watery part is on top giving low readings. The high acid at the bottom eats the bottom of the plates-not good) Try to keep the mix even.With the caps on, tip the battery up on its end and leave it for five minutes, then tip it up on the other end and wait five minutes, then when it is upright, wobble it back and forth some. Now take the SGs again.To prevent stratification while on Float, you need to give the battery a shot of higher voltage every so often.It won't spill if I do that?

Puttin wrote:Those readings are fairly close to full charge. Did you add any water the day before you read them? That can have a negative effect. They should be charged before you water them and again after.Here's more info:Battery infoHope this helps.No, didn't add water recently. I get that it's fairly close to full, but I've read how important it is to be 100%. Sounds like just getting close is a recipe for a short battery life.

I am not sure the angle BFL is saying to use, but I would not use 90 degrees, perhaps 45.In my experience those plastic hydrometers like the EZ red are not accurate nor precise. If there are any bubbles that stick to the float, the reading is invalid, and the lower the SG, it seems more bubbles will stick to the float.Do a couple bulb squeezes before trying to take a reading. i like to pull from one side of the cell and push to the other side of the cell a few times if the battery has been sitting.Maintainers have a loyal following, but some seem to think they can fully charge a battery if left on Long enough. They should only be put on after the battery has been fully charged by a more powerful charging source which can hold the battery in the mid 14v range for 2 to 4 hours.Interstate has never manufactured a battery. They are a battery marketer. Maximum profit is the name of the game. They best battery does not yield the best profit.Beware of marketing and loyal subjects of marketing.Marketing = dishonesty, for maximum profit.

Finally bought a battery hydrometer, need help with results

58 Replies

RDMueller
Explorer
Oct 05, 2015
MEXICOWANDERER wrote:
800 ma @ 18vdc OCV per 100 AH is my guideline. Transformer based wart.

I actually have an 800mA 18vdc wart. I guess it would be perfect for a group 27 battery, maybe a little big for a group 24, but I could try it next, maybe just not leave it too long.
MEXICOWANDERER
Explorer
Oct 05, 2015
800 ma @ 18vdc OCV per 100 AH is my guideline. Transformer based wart.
RDMueller
Explorer
Oct 05, 2015
Update: looks like I hit the ceiling with this wall wart. Another 36 hours later the charging voltage is unchanged at 14.25V and SG is still 1.250. I guess this 300mA wart just doesn't have enough power to get the voltage any higher, even though unloaded it is about 18v.

So, moved on to another wart I found. On this one the label says output is 12VDC and 1A. I measured the unloaded voltage at 16. Connected it to the battery and within a few minutes the voltage was steady at 14.7. Now we may be getting somewhere!
westend
Explorer
Oct 04, 2015
RDMueller wrote:
Charging voltage this morning is up to 14.25V from 13.3 last night. This evening will be 48 hours and I'll take the SG then. Sounds though like something this small, only 300mA, will never get the voltage high enough to achieve a full charge. Still though, interesting to see what happens!
Stay with it up to your target voltage and run it for an hour or until you go .10 V above.

FWIW, last night I had a reason to make sure both my back up car jars were fully charged. Starting voltages were at 12.3 V and 12.6 V. As far as I know, these are identical model batteries but one is two years older. One battery was connected to a wheeled Exide shop charger and set at 2 amp output. The other battery was connected to the Wall wart at 500 ma rating. I unpowered both chargers this morning. The resting voltage now is 12.80 V on one and 12.81 on the other.
RDMueller
Explorer
Oct 04, 2015
Charging voltage this morning is up to 14.25V from 13.3 last night. This evening will be 48 hours and I'll take the SG then. Sounds though like something this small, only 300mA, will never get the voltage high enough to achieve a full charge. Still though, interesting to see what happens!
pianotuna
Nomad III
Oct 04, 2015
From what I've been able to glean about charging rates, to equalize a battery one needs to provide enough amperage to get to the c/20 rate. That works out to 5 amps per 100 amp-hours of capacity.
BFL13
Explorer II
Oct 04, 2015
It's those darned watts. The low amp but high voltage charger can't get the batteries all the way up because it lacks the power to keep the amps going at the higher voltage.

I do know my manual trickle charger "stalls out" and can't get the battery any higher in voltage when it theory the voltage should just keep climbing till I shut off the charger. A bigger amp (more watts too) charger will get the battery higher before it stalls out.
MEXICOWANDERER
Explorer
Oct 04, 2015
The warts are for storage. Buzzing a top charge every 4-6 weeks is still highly recommended. 5% amperage of total amp hour capacity until voltage reaches 15.0 then resume the wart. Wish somone out there was smart enough to realize this is the protocol flooded batteries scream for.

I like transformer based 15 volt warts. They are near indestructable for storage charge. If I am going to spend 65 dollars on a charger it is going to be a Megawatt. A sealed srorage charger might be worth the high bucks if it is used in the rain for a boat or ski doo. But for a single battery wintering in a basement seventy bucks is a bit rich for my blood.
pianotuna
Nomad III
Oct 04, 2015
RD welcome to the club. Battery charging is partly an art form and partly "dancing on the needles".

Charging lead acid cells is dependent on literally hundreds of variables. Not the least of these is that no two cells are ever created totally equal. It's as bad as snowflakes...i.e. possible to have 2 the same but really rather rare.

RDMueller wrote:
It's just when you get to batteries and charging in particular where there's a lot I still don't understand.
RDMueller
Explorer
Oct 04, 2015
That clears up a lot! A Megawatt and and an ammeter is the plan. Also, the actual batteries I will dry camp with will be the T-105's. All this messing around with wall warts and the Interstate 24 really is more about education than anything else. I have a really good grasp of electrical in general, both AC and DC. It's just when you get to batteries and charging in particular where there's a lot I still don't understand.

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Finally bought a battery hydrometer, need help with results

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