Team-BHP (https://www.team-bhp.com/forum/)

-   Technical Stuff (https://www.team-bhp.com/forum/technical-stuff/)

-   -   Ownership Review: Bosch C7 Battery Charger (https://www.team-bhp.com/forum/technical-stuff/184814-ownership-review-bosch-c7-battery-charger.html)

This is a short ownership review of Bosch C7 Battery Charger, I feel this will benefit members with AGM car batteries.

The other day I had to jump start my S class due to dead battery. My car battery is pretty healthy (I think), it is just that the car was sitting in the garage for a few days and on that day I was doing some marathon vacuuming and cleaning so the battery went flat. It happened at home, so it wasn't such a big deal.

This lead me to research this battery topic and here is the gist of it:
1. These luxury car batteries (AGM type) cost 40-50K, enough motivation to extend their life
2. Dead batteries can cause weird issues in these complex cars
3. Fully charged batteries last long and deeply discharged batteries die real quick. Keep the batteries fully charged at all times. Don't let them discharge deeply and never let them stay deeply discharged for long periods.
4. Alternator is only designed for top-up charging and can kill itself trying to charge a deeply discharged (or a faulty) battery
5. The battery life will be shortened significantly if the car is used sparingly and only for short trips.

So it is obvious that I should try to keep my battery charged at 100% as much as possible. I bought Bosch C7 battery charger from Amazon India for Rs 7000, they also have a cheaper C3 model. I am happy to report that it is a high quality product and very simple to use. Needs an electric socket where the car is parked, so not sure about apartment parking lots. These are called "smart/intelligent chargers" and are safe to use.

The actual review isn't much because it is a very simple to use device. Connect +ve and then -ve terminal, select you battery type (flooded or AGM) and it will charge the battery showing indicator for 4 stages of charging (<25%, <75%, <100%, maintenance charge). The device is very sturdy typical of Bosch products and has the state of the art technology as far as battery chargers go.

Ideal for cars with expensive batteries that are not daily drivers. My current battery is 5 yrs old, I guess it will pay for itself by extending the battery/alternator life. It can also be used to start car with a dead battery, though I have not tested this feature. It has 7 amp output, may require overnight charging if your battery is fully discharged.

Here are some photos:

Source: amazon.in


Battery always starts with step1 (0-25-50%). It will move on to step2 within 1 minute or so if the battery charge is above 50%.


Step2 (50-75%)


Step3 (75-100%)


Step4 (100% maintenance charge)

Thanks for sharing, i was also on the look out for something similar. Let me check amazon for the C3 model also. Thanks for sharing.

Coincidentally I just bought one of these a couple of days back from Amazon. I've used B&D (UK), Battery Tender (US), CTEKs (Swedish) but this one is a premium piece of kit matching the CTEKs. All these are microchip controlled.

The Bosch C7 is highly recommended. The only advantage the Battery Tender and CTEKs have over the Bosch is they have temperature compensated charging which IMO is not a "must have" but a "nice to have" feature.

PS - I agree completely with you when you say alternators are used for top up charging. I say their function is to maintain a battery not revive or charge a deeply discharged unit. The alternator diodes could fail if this is attempted. Of course I am aware of the 'take the car for a long drive' technique after a jump start but would never recommend this method of reviving a dead battery unless in an emergency.

I am also considering this: http://www.amazon.in/Compact-Portabl...ct_top?ie=UTF8 The price is a bit difficult to swallow but one of these jump starters could save you from being stranded in the middle of nowhere.

I dropped the idea of buying such a product because:

1. At the time you want it to put it to use, it should be holding sufficient charge. Not likely as I am not going to keep track of its charging.
2. The durability (esp due to battery) is doubtful.
3. Most claims of ability to start heavy engines are suspect.

Keeping a good quality jumper cables is cheaper, reliable and durable (unless of course you go to places without another car in sight).

I agree with you.

The gadget costs approximately 2x as much as my car battery. Hence my hesitation. I do carry jumper cables and a battery charger (the compact Battery Tender 1.25 A which is slightly larger than a laptop power adapter) when travelling out of station.

But the real reason this gadget caught my attention is I sometimes drive long distances at night with the family and would not like to be stranded somewhere. My better half would certainly not be pleased in case of a breakdown. lol: The gadget starts up to 6L petrol and 2.5L diesel engines as per the manufacturer. Feedback on the gadget is encouraging. There are other makes too including NOCO.

https://www.anker.com/products/A1501071

There's a catch when using this device - your car battery needs to have a residual charge of between 1 and 50% i.e. it should not be totally dead for the jump starter to be effective.

So, I am still mulling over it. Not sure I can justify the cost just yet.

I saw many variants of this at the canton fair being sold for anywhere between INR 2,000 - INR4,000 So absolutely no point spending that kind of money on it. You could buy something with similar specs from aliexpress for less than half the price.

Could you elaborate on this please.

Regards
Sutripta

I'm no expert but I am guessing it is because alternators are designed for a certain amount of electrical load. A battery that is drawing current for a prolonged period (instead of just top-up) can overwork the alternator. I suppose you can reduce the load on the alternator if you switch off all other electrical systems like AC, lights, music player, etc. when recharging a battery that went flat. If the battery is not holding charge, then the alternator has to perpetually work beyond it's safe range to fill this 'pot with a hole'.

Knowing the inflammable and explosive nature of high capacity Li-ion batteries which these jump start gadgets use, I frankly wouldn't want take a risk just yet & keep an unknown Chinese brand in my car.

Question is will the alternator be 'killed'/ ówerworked' etc if it is generating its rated output for a length of time. Is rated output beyond 'safe range'? Something a bit more authoritative than 'its commonsense' etc.

Regards
Sutripta

Yes it could, based on articles and and messages on different internet fora

So, I think what he meant (and I do agree with his contention) by "common sense" is why take a risk with alternator damage when you can use a reasonably priced charger (which is far cheaper than alternator repair in an Mercedes Benz S-Class or even a new battery for that car) to bring the battery up to its full state of charge. This risk to the alternator is more pronounced if the battery is faulty and not accepting a charge.

Here's more advice from a well known AGM battery manufacturer:

https://www.optimabatteries.com/en-u...dead-batteries

PS - One of the good things about using a smart charger is it warns you if the battery is faulty and a complete goner or it can be revived.

:)^^^
Question is not on battery chargers vs driving the car. (Driving a vehicle just to top up a battery offends my (efficiency related) sensibilities. Also Charging a deeply discharged battery using a vehicle alternator is detrimental to the health of the battery. Certainly better to use a charger. (Maybe the reason for Optima's warning :) ) Incidentally I have/ had 3: a local (Elak, a CTEK, and a homebrew UP controlled intelligent one, in which the SMPS part gave up the ghost a long time back).
So the question once again becomes 'will an alternator get killed' if it is working at its rated output, and can it work beyond its rated output? And why? Once again, something beyond anecdotal 'evidence' and 'common sense'.

Regards
Sutripta

Only the alternator's manufacturers i.e. the OEM's suppliers can give you an authoritative answer. Knowing the manner in which OEM part specs & test reports are kept confidential those details will be hard to come by. Ask either the OEM or the supplier & you'll hit a stone wall.

So, in the absence of these technical details, why second guess what Optima or others have advised unless we possess some information or experience that indicates, or better still proves, that their advice is only partially correct or completely wrong?

I for one believe Optima's advice is based on scientific and other evidence collated over a period of time. And I'd rather go by that than play guessing games and take risks with my expensive alternator/battery. :)

No the alternator will not fail. Lets first agree and define, "alternator" = alternator + rectifier.

Its output current or maximum power is field current limited in nominal conditions and magnetic saturation + winding resistance limited under duress (duress causes heat, in turn, causes increased winding resistances).

BUT, whether the diodes downstream in the rectifier stack is able to work under extended overloads, without exceeding the silicon junction temperature of 150 degrees (fail threshold) or so, unconditionally, is entirely an engineering question many OEMs would try to avoid answering. Why? Costs. Lesser metal for heat-sinking, smaller diodes for the "job, acceptably done". For rated power output, nothing goes bust if the airflow/natural convection is not blocked.

So if it fails as a whole, the alternator part is likely still alive with only the rectifier bust.

In a good design, it will survive, as increased temperature of the entire assembly will cause field excitation to be reduced in a closed loop. (Now you are almost offended because I am borderline "jargon" ing, so will stop here.:D)

^^^
Hi LL,
Broadly agree, but ...
Maybe oneday we'll have a discussion on electronic component failures in alternators, esp Indian (Lucas??) ones. OT for this thread. In fact (unfortunately) not really a discussion for this forum.

Regards
Sutripta