How Accurate Is The Voltage Reader On The HDS

Well I got my HDS 8 wired up, and I’m having an interesting situation. My battery charger has been acting wonky for years (charging to 100% in half an hour, running the volts on the batteries up to 15, fluctuating all over, etc). So I thought it may have fried my batteries (two of which, my trolling motor deep cycles, I’ve been using for as long as Ican remember). When I hooked my HDS up it confirmed my thoughts, saying that the voltage was anywhere from 11 all the way down to 8.5 depending on the battery I hooked it up to. Well I took one of the deep cycles in to Batteries Plus to get it tested, and it passed! Full 12 volts and 600CCA, when the battery’s only rated for 575! But the HDS still says it’s at 11 volts. So I’m assuming the HDS is just reading it incorrectly? Keep in mind I know literally next to nothing about electricity and wiring and all that jazz, so I have no idea what’s really going on.

My buddy thinks that since the batteries are older they won’t charge up to 12 volts fully, but as far as I know they would, they just wouldn’t hold that charge nearly as long? I thought a fully charged 12v battery should actually be up around 13 volts? Thanks guys!

If I remember right a full battery is 12.6V ,also some where it was said that the HDS reads voltage after the processor so it is a little less than the acual battery volts. I’m going to check my battery with a meter and see what I get. Get a meter and check right at the battery if it’s moving around then it’s battery related ,if not its probbably wireing related.

Stan

The answer is not real accurate,the battery was 12.36VDC on volt meter HDS 8 on ram by council show 11.5 VDC HDS 7 up front said 11.3VDC so don’t worry about it,I guess I won,t turn on meter to monitor voltage,as I had thaught about,as long as the motor starts when needed ,thats all I’ll worry about,which it always has.heres some interesting artice on batteries

http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf

http://scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

Stan

Alright well I’m glad to hear that my HDS isn’t performing worse than the average unit! And thanks for the charts those are very helpful, I didn’t know that a battery will have a higher voltage while being charged as opposed to draining (I mean obviously besides if it’s drained significantly), so I guess my battery charger is working after all? Thanks for the help guys!

There are also a couple different voltage options on the HDS that you can monitor. One of them will show voltages way out of wack, and one will be pretty close, but I don’t remember which is which. I believe you also lose some voltage over the wire, so the further the run, the less it will show, but I’m not an electrician so I could be totally wrong.

Temperature of a battery will also affect the full charge voltage reading. Didn’t see any mention of that in the link. The colder the battery, the lower the charge reading. And you are correct, the resistance of the wire will affect the voltage reading.

You could have a bad connection somewhere too, maybe at the fuse. Check the voltage at the power cable where it goes into the display.

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You could have a bad connection somewhere too, maybe at the fuse. Check the voltage at the power cable where it goes into the display.

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My hds 8 had enough of a good connection to run the sonar just fine. But it wouldn’t get a fix on the GPS. The connections all looked good. Did a soft reset, no dice. Then updated the system from Lowrance. Still no dice. For the kicks cleaned the connections and re connected and now it works perfect again. Electrical stuff can be bizarre. It amazes me it had enough to run the unit but not power up the GPS, fairly common I guess.