I am lost with this charging system problem

[soupersupra]

So couple of years ago I bought a new deep cycle battery in hopes of getting rid of lights dimming when i turn my sub up ( helped for a little while). This is for my 88 turbo and last year at the end of the year I started having problems with not charging right but alternator was fine. Had it checked out and was good... so this year I got my car out and got a new more powerful deep cycle battery and a drift motion 140 amp alt. Now I've done the big 3 upgrade for the grounds and the alt power. Well it seems to not be charging right still. I start it in the morning and it charges from 14.4 to 14.5. Then car warms up and it sometimes will charge at 13.0 and 13.4 with all components off. A couple days ago I noticed that the 100amp alternator fuse under the hood was blown so I replaced it. Before this it seemed like it wasn't charging right but it had more charge than it does with it changed. I was at 13.9 to 14.0. I've checked all fuses and such too. I should have plenty of power for everything and then some.
Also when I hit the brakes voltage drops from 13.4 down to 12.6.
Also at idle at times it sits at 13.0 till I blip the gas. Anyone have any ideas?

 

[Nick M]

Voltage going down can be because current is flowing easily. It doesn't necessarily mean it isn't charging. The 100 amp fuse circuit needs to be inspected for a direct ground, even if intermittent.

 

[jetjock]

Deep cycle batteries. Now that's entertainment.

 

[Nick M]

Deep cycle batteries. Now that's entertainment.

I figure why bother.....

 

[suprarx7nut]

OP: My guess is that your sub is just drawing too much power. If the alternator is new, wiring is new and battery is new you may just be at the limits of the factory set-up. Deep cycle batteries aren't necessarily good for your situation. Deep cycle batteries tend to allow more discharge of the battery, but can provide less current for momentary loads (like a high powered amplifier). Your new battery may be a part of the problem, but I'm not sure how you would easily test that theory short of trying a regular battery.

What kind of power are you running through the amp?

Deep cycle batteries. Now that's entertainment.

Apparently I'm with stupid because I don't get it. A deep cycle battery won't help a weak charging system or a large temporary load (subs), but they exist and serve a purpose, no?

What's entertaining about deep cycle batteries?

 

[Nick M]

Deep cycle batteries aren't necessarily good for your situation... A deep cycle battery won't help a weak charging system or a large temporary load (subs).

Apparently I'm with stupid because I don't get it...What's entertaining about deep cycle batteries.

Think about it. Also, he needs an amp probe. If he sees 12.6 volts and 98 amps....well, that answers the question. If he sees 12.6 volts and 0 amps, then come back.

 

[Kckazdude]

Also of note is that deep cycle batteries are not meant to be charged at high amperage rate as an alternator. The plates literally degenerate making the alternator work harder to keep up with the electrical demand that the battery cannot keep up with.

My advice, ditch the deep cycle battery and get a good AGM battery in a 48 case series or an Optima battery if you have money to burn.

 

[jetjock]

What Nick said. His use of them is entertaining.

Also it's unlikely what the OP bought were true deep cycle. More likely a hybrid typically used in marine and cheap RV installations. They say "deep cycle" on them but aren't. True deep cycle (at least the smaller ones) are used in things like golf carts and usually limited to 6 volts. Doesn't really matter though because such an approach to his problem makes no sense whatsoever.

 

[suprarx7nut]

Think about it. Also, he needs an amp probe. If he sees 12.6 volts and 98 amps....well, that answers the question. If he sees 12.6 volts and 0 amps, then come back.

What Nick said. His use of them is entertaining.

Also it's unlikely what the OP bought were true deep cycle. More likely a hybrid typically used in marine and cheap RV installations. They say "deep cycle" on them but aren't. True deep cycle (at least the smaller ones) are used in things like golf carts and usually limited to 6 volts. Doesn't really matter though because such an approach to his problem makes no sense whatsoever.

Ok, but that's a rather minor misconception. Deep cycle batteries seem to be common in the car audio world because they're good for secondary batteries in high power systems where the battery will actually be drained or near drained during a contest or something. Thinking they're going to help the charging system in a car with a powerful amp is just a missed connection in their purpose.

::shurg:: I don't know, I don't see the entertainment so much as an ill-informed person who's at least gone to the trouble of taking voltage readings to try to sort it out.

Also of note is that deep cycle batteries are not meant to be charged at high amperage rate as an alternator. The plates literally degenerate making the alternator work harder to keep up with the electrical demand that the battery cannot keep up with.

My advice, ditch the deep cycle battery and get a good AGM battery in a 48 case series or an Optima battery if you have money to burn.

Die Hard Platinum were my go-to AGMs, but now they're discontinued. How makes a good one these days?

 

[Kckazdude]

East Penn and Johnson Controls still make the most consistent batteries that I have seen. This seems to vary by region and brands. This all seems to be a moving target as continuing profits is the order of the day.

 

[Nick M]

How makes a good one these days?

The behemoth known as Johnson Controls still makes really good stuff, if the retailer wants an expensive battery. They even bought up Optima (way overrated) a decade and a half ago. I would have to crib Wikipedia to see the sale date.

 

[Nick M]

So, does the OP have access to an ampere clamp that plugs into a Fluke? Maybe Centech makes a low dollar version sold at Harbor Freight. I am not sure. The basic idea is to crank up all your accessories. Blower motor on high, etc. etc. Then measure current flow.

 

[soupersupra]

I guess I'm mistaken with deep cycle. It is an agm battery I bought. I had a standard battery in it for a little bit before I got this battery and it was worse. I'm not running more than 500 watts max for an amp to my subwoofer and maybe 200 to my speakers. Rockford 1000.1 bd to alpine type r 12 and Rockford prime 300.4. BUT that aside I drove the car this week and watched what it was doing charging-wise. And only on start up I found the voltage to charge at 14.2 then it would go and it was kind of all over the board... some instances it would charge at 13.8 and stay there no matter what I did and other times it would be charging at about 13.2 to 13.4 after driving for awhile. It just seems a little strange. I suppose I'll check my other supras charging habits and see what that comes up with.

 

[soupersupra]

I don't have access to a clamp but I'm going to grab one soon.