over under damage?

[desert_sailing]

I have 2- 35amp sealed deep cycle batteries wired to give me 70 amps total. If I am not entirely broken, that comes to 840 watts with 420 usable?

I picked up a 12v electric blanket the other day to test. Unfortunately it does not have multi setting and must have a built in theromostat that I  can NOT adjust. I also cant just shut off and have to remove from the outlet.

It was only 20 bux and super snug. I like it alot but with my capacity.. 8 hours will entirely deplete my batteries.... which on the first night of usage it did. I figured I would wake up and pull the plug with one eye open..but I was super content surrounded by the warmth.

When I finally did get out of bed the voltmeter was reading 11.9 and nothing was plugged/running off the system...12.2 is half way I believe? So I was a bit under and worried if I damaged the batteries. I plugged the solar panels up but due to the smoke from regional fires it was a super slow charge.. took me basically 3 days to make serious gains using only a 100 watt panel.

Yesterday when I checked the recharge progress the meter was reading 12.9 volt... I thought the  charging cycle would end to prevent overcharging?...I thought it had shutoff before automatically but now it doesnt appear to do so as the little icons show a flashing arrow from the sun and a rising battery bar flashing.

So I am curious if I have damaged the battery at all either  by dropping so "low" or if I have damaged by going too "high"?

Is there a standard maximum high for a 12 volt or does it vary with battery manufacturer?

I unfortunately do not yet have a battery management system per se and can't see the actual amps.

Just curious if anyone had a quick answer..

Thanks!

 

[DLTooley]

Ditch the heated blanket, just get another regular one or a sleeping bag. I sleep clothed, washing and changing mid afternoon when it’s warmest.

Batteries charge at a higher voltage, that’s normal. The quality of charge controllers vary considerably. I like the Victron for the info it gives.

 

[desert_sailing]

Ya..the blanket was a tester for sure.. maybe one day I will have energy to run it.. if not maybe someone down the line will need it.

Batteries charge at a highr voltage... but does that mean they can store more? I am going to have to find some articles out there so I fully understand I guess.

If 12 volt batter is reading 12.9 when idle... when does it qualify as overcharged and dancing along the damaged line.?

 

[highdesertranger]

you never mentioned how high you got it?

yes, the maximum varies with each manufacturer.

highdesertranger

 

[desert_sailing]

It did say 12.9 without anything going in or out//just sitting there.

 

[jonyjoe303]

for lead acid batteries, you need at least 14.4 volts to charge. If the max your seeing is 12.9 volts, the battery isn't even being float charge (13.7 volts) in other words the battery wasn't even charged. To fully charge the battery it has to reach 14.4 volts and stay there for several hours (absorb) until the amps going into the battery drop to 100 milliamps. The 12.9 volts you read is just surface voltage, as soon as you put a big load on the battery, voltage will drop quickly.

The battery won't last long if you don't fully charge every day. With a 100 watt panel it might not be practical, especially now that winter is almost here. If you can get a larger panel, at least 240 watts, that will give you at least 12 amps of charge power. Or maybe use the alternator to augment the solar panel.

You can drain the battery below 12.1 volts several times (3 or 4 times) before they lose capacity, but when you do drain them, you need to quickly charge it back up to 14.4 volts the next day, don't let them sit in a depleted condition too long.

 

[desert_sailing]

Thanks for the info... so my battery is  fully charged when it reads 14.4?... I dont understand then why the diagram shows 12.73 as 100%?

The input I have seen on my charger with panels deployed is usually 13 something.. it is just a 10 amp controller.

 

[highdesertranger]

ok I think we are all confused here.

desert the chart that jonyjoe posted is for a rested battery. that is after a battery has sat without being charged or discharged for hours. we used to let them set overnight. this is one reason why voltage is a poor indicator of SOC(State Of Charge).

now the 14.4v is what your charge source needs to get your battery to. 13 something ain't goin to cut it. if that's all you are getting to you are undercharging your battery. is your controller adjustable?

highdesertranger

 

[desert_sailing]

So the voltmeter is reading 12.6 right now without any charging or discharging for 2 days now.

I do believe the controller is adjustable. The manual is terribaaad. It is one of those 100 watt Thunderbolt kits from harbor freight... IKR...

I will go over the manual again and see what I can glean from it.
I obviously need a better way to determine my soc than this voltmeter set up.

 

[highdesertranger]

12.6 after resting for 2 days is not great, however it is not terrible. do you have anyway to get it up to the 14v+ for a good charge? are these sealed batteries? what are the chrage rate specs? highdesertranger

 

[desert_sailing]

Thanks for taking the time. I unfortunately threw away the paper work for the batteries but I can find it online I am sure. Ill have to get on that so I fully understand wat the heck I am doing

I have seen the voltmeter read 14 something at rest when I first charged them up..but I saw that chart before and assumed that  12.7 was full.  I have it taped to the batteries so I have it at the ready... I am understanding then that 12.7 isn't actually full and it should really read 14 something?

They are sealed batteries.. deep cycle.

 

[Sofisintown]

The blanket you are using is 45 watt and it pulls 3.75 amps/hour.
In 10 hours your 2 batteries will be at just below 50%, if you start with fully charged batteries, and do not run anything else during the blanket use.

If you start with your batteries NOT fully charged, or if you have lights on etc., you will deplete the batteries faster.
It is not a big deal if you use the blanket for a couple of hours, though.

 

[desert_sailing]

230am and just found this little snippet.

"All Lead acid batteries (Gel, AGM, Flooded, Drycell, etc) are made up of a series of 2.2 volt cells that are bridged together in series to reach their final desired voltage. For instance, a 6 volt battery will have 3 cells (3 x2.2= 6.6 volts), a 12v battery for a motorcycle will have 6 cells (6 x2.2=13.2 volts) and so on. That 2.2 volts is the fully charged, straight off the charger number. The actual resting voltage, or the voltage a battery will settle at 12-24 hours after being removed from the charger is closer to 2.1 volts per cell, or about 6.4 volts for a 6v battery, and 12.7 volts for a 12v battery. These numbers assume 100% healthy cells, and may vary a bit lower for older batteries."

I understand that while charging and for awhile later the voltage can/will read higher than 12.7 but after some time it should settle to 12.7. Ok..so if after 12 hours the voltmeter is still reading over the 12.7 does that mean the battery is overcharged and could be an issue?

Ima have to check for it in a few hours... long night painting...

 

[highdesertranger]

12.7v after a 12 hour rest is not over charged. highdesertranger

 

[jonyjoe303]

To overcharge your battery you would have to charge at more then 15 volts, right now the battery might be at 60 or 70 percent, if you reach 14.2 volts while charging it might be at 80 percent, at 14.3 volts you would be around 90 percent and at 14.4 volts your about 95 percent, the other 5 percent can take hours at 14.4 volts. Lead acid batteries take their time to fully charge.

The 12.7 volts you read is just the surface voltage from charging at 12.9 volts, as soon as you put a load on the battery the battery will drop in voltage. A fully charge battery will also drop in voltage but not much.

Its almost impossible to overcharge a lead acid with solar power, the sun will go down before it even reaches a full charge.

I highly recommend you get a coulombmeter for your battery, they count the amps going in/out of your battery. With it you know if you use 20 amps, then tomorrow you need to add at least 20 amps to be full again. counting amps is more accurate then voltage on lead acid. TK15 coulombmeter cost about 30 dollars on ebay, its great for monitoring your battery. Since it reads the voltage directly from the battery, you would know if your reaching 14.4 volts.

 

[Weight]

2 x 35 amp battery. Not 70 amps. battery are rated by amp hours. That is different measurement than 'how many amps'

 

[desert_sailing]

2- 35 amp batteries wired in  parallel does not equal 70 amps??

 

[highdesertranger]

"Its almost impossible to overcharge a lead acid with solar power,"

while this is true it is because the charge controller regulates the charge.

"the sun will go down before it even reaches a full charge."

this is not true if you have enough watts.

"2- 35 amp batteries wired in parallel does not equal 70 amps??"

well you are not using the right terminology, they are not 35 amp batteries. they are 35amp hour batteries. minor technical issue. it should read,
2-35amphr = 70amphr. or 35ah x 2 = 70ah is how I write it, I am really not sure how exactly you are suppose to write it.

highdesertranger

 

[desert_sailing]

"Its almost impossible to overcharge a lead acid with solar power,"

while this is true it is because the charge controller regulates the charge.

"the sun will go down before it even reaches a full charge."

this is not true if you have enough watts.

"2- 35 amp batteries wired in  parallel does not equal 70 amps??"

well you are not using the right terminology,  they are not 35 amp batteries.  they are 35amp hour batteries.  minor technical issue. it should read,
2-35amphr = 70amphr.  or 35ah x 2 = 70ah is how I write it,  I am really not sure how exactly you are suppose to write it.

highdesertranger

Thank you for clarifying.

I have indeed seen "ah" as the correct way. I need to get up to date about terms on some of this so I am clear. Maybe that is why I have had to return sooo many items and get the right item.

I guess in the meantime I can just keep juicing the batteries and hope that the charge controller stops when I am full...LOL..or untl i get one of those coulombmeter things.

Appreciate the info everyone.. thank you for taking the time.

 

[DLTooley]

Welcome to the learning curve of solar. Just to clarify, the charging voltage is higher than the fully charged voltage of your battery. If you’ve just disconnected it will be higher as well, until it rests. Temperature matters too.

Another thing, amp hours as a designation of capacity is a bit misleading. It is very common in the 12v world, but actual power is in Watts. Volts x Amps = Watts.

You’ve probably seen adds for some many thousands of amp hours in a battery charging device or such, but that is misleading as the voltage is much lower.