Battery chargers.

[PaulJ2]

Maybe a question for Mex.
Stone dead 12 volt battery on my Prius. Gone for a week and door ajar causing dome light to drain battery.
Brought out 2 different battery chargers,neither one would put out any voltage. One an automatic 10 amp unit and the other 1.5 amp battery charger/maintainer unit.
Measured voltage at the dead battery was .3 volts.
I then drug out my 30+ year old 1 amp motorcycle manual charger. Worked fine! Is this some safety thing so you can't spark the two clamps together?
I guess they have to see a couple volts before they will operate.
Geeeez!

[BarabooBob]

I had a 1999 Ford Ranger that would not start if the mounted battery was dead. I tried jump starting with my other vehicle and nothing would happen. I unhooked the dead battery, and the truck started right up. I contacted the local Ford stealership and they said that the truck could tell that the mounted battery was dead. It didn't make sense to me, but, I am not an engineer.
Had the friend call me and had the same problem. He unhooked the dead battery and it started.

I have a couple of smart chargers and if the charge is low enough, they will not work. I also keep a stupid charger on hand to start the process.

[PaulJ2]

PaulJ2 wrote:

time2roll wrote:

PaulJ2 wrote:
Interesting is that the instant i connected the good charger i jumped into the car, turned the key and it started right up.
The now 12 volts activated some relays connecting up the 276 volt battery and the engine started immediately. Just needed 12 volts to operate some relays i guess.

Good reason to have a jump-box handy. Especially if it happens away from home.

BTW check the resting voltage of that battery in the morning after a few days of use. Or take it down and have it load tested. Running flat dead could have wiped out half the capacity.

I agree, a very good reason to have a jump box. It's on my list.

BTW probably no good way to do a load test, as it is a small sealed type battery. Looks like a motorcycle/ATV/UTV battery.

[pnichols]

Several years ago I began carrying a full size 12V AGM vehicle battery in a regular battery box in the trunk of our daily driver. This is in addition to jumper cables that I carry in every vehicle. Since AGM batteries don't discharge very fast when stored, I only have to top-up-charge the AGM battery about once a year.

I feel that it's inconvenient and unnecessary to have to call ERS for a dead starting battery. Carrying the extra AGM battery along is an easy way to keep things simple.

[filrupmark]

I had the same problem . Broke out the old Montgomery Ward charger and Walla !!!

[PaulJ2]

time2roll wrote:

PaulJ2 wrote:
Interesting is that the instant i connected the good charger i jumped into the car, turned the key and it started right up.
The now 12 volts activated some relays connecting up the 276 volt battery and the engine started immediately. Just needed 12 volts to operate some relays i guess.

Good reason to have a jump-box handy. Especially if it happens away from home.

BTW check the resting voltage of that battery in the morning after a few days of use. Or take it down and have it load tested. Running flat dead could have wiped out half the capacity.

I agree, a very good reason to have a jump box. It's on my list.

[pianotuna]

Hi,

That does not work with either of my chargers. One is a Vector, and the other is a Harbor freight (which I thought was a dumb charger).

JaxDad wrote:


Even “smart” chargers will work IF it has the “engine start” or “booster” function.

I have several such chargers, in the “boost” mode they just put out a 14.5’ish volt full rated current regardless of battery voltage.

The best of both worlds.

[time2roll]

PaulJ2 wrote:
Interesting is that the instant i connected the good charger i jumped into the car, turned the key and it started right up.
The now 12 volts activated some relays connecting up the 276 volt battery and the engine started immediately. Just needed 12 volts to operate some relays i guess.

Good reason to have a jump-box handy. Especially if it happens away from home.

BTW check the resting voltage of that battery in the morning after a few days of use. Or take it down and have it load tested. Running flat dead could have wiped out half the capacity.

[wa8yxm]

Many Smart chargers today need voltage or they wont' output if the battery is "STONE DEAD" they can not tell it is even there.

I have a "Jump Starter" pack. also a "Jump starter" type charger.. (I've never used that feature on the charger).

Hook the jump pack long enough to let a surface charge transfer THEN kick in the charger and once its showing current flow pull the jump pack and recharge IT per the istructions.

[Sam_Spade]

JaxDad wrote:

I have several such chargers, in the “boost” mode they just put out a 14.5’ish volt full rated current regardless of battery voltage.

The best of both worlds.

That can be a BAD plan.

Without testing the battery first, there could be a shorted cell....or two....and "boost" or start mode is capable of supplying a LOT of current, which could cause some REALLY nasty things to happen.

[JaxDad]

beemerphile1 wrote:

LittleBill wrote:
smart chargers need to see a minimum amount of voltage to turn on. usually because its a bit dangerous to charge a 100% dead battery

^This

Parallel a good battery with the dead one. After the charger starts disconnect the good battery.

Even “smart” chargers will work IF it has the “engine start” or “booster” function.

I have several such chargers, in the “boost” mode they just put out a 14.5’ish volt full rated current regardless of battery voltage.

The best of both worlds.

[PaulJ2]

time2roll wrote:

camperdave wrote:
It's good to keep the old dumb stuff around sometimes, for things like this. That's what I tell my wife about me anyway...

My wife's Ford Fusion hybrid wouldn't start a while back because of a dead starter battery. It amused me that there's 300v of lithium sitting in the truck, but the car wouldn't start because the lead acid battery under the hood was dead. She didn't find it amusing.

Getting to be a bigger issue with all the telemetrics that never shut down on these new cars.

Especially frustrating with the EVs that really need a deep cycle battery since zero need for the start surge.

I think the OP has the answer. Although I am surprised a dome light did it. Even my old 2001 F150 will cut all power at about 30 minutes if this is detected.

Yes, my 2004 Chev truck shuts it's dome lights off after 10 minutes, however this was a 2001 Prius and i guess they had not thought of that back then.
Interesting is that the instant i connected the good charger i jumped into the car, turned the key and it started right up.
The now 12 volts activated some relays connecting up the 276 volt battery and the engine started immediately. Just needed 12 volts to operate some relays i guess.

[beemerphile1]

LittleBill wrote:
smart chargers need to see a minimum amount of voltage to turn on. usually because its a bit dangerous to charge a 100% dead battery

^This

Parallel a good battery with the dead one. After the charger starts disconnect the good battery.

[pianotuna]

Speaking of Mex has anyone heard a peep from him? I tried to email-but received no response.

[Sam_Spade]

PaulJ2 wrote:

I guess they have to see a couple volts before they will operate.
Geeeez!

You answered your own question.
What do you intend to do NEXT ?
Shopping for a new battery would be good.

Exact fit batteries for Prii are hard to find sometimes.